3 76
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
TABLEOF ANALYSES Leach After Final Final Ashes Liquor Causticizing Hydroxide Sulfate SUBSTANCE Per cent Per cent Per cent Per cent Fer cent Sulfate . . . . . . . . 2 . 9 0 3.36 3.14 Trace 99.05 Carbonate.. . . . . 4 . 5 0 5.22 0.25 4 Nil Hydroxide.. , . . , 4 . 2 5 4.95 8.56 96 Nil ...... ... Chloride. 0.02 0.02 .. I,EACH LIQUORFOR A TYPICAL RUN,JUST BEFORE CHANGING THE TUBS Tub No.. . . . . . . . . . . . . . . . 1 2 3 4 5 Total alkali (as K2COs), percent 0.33 1.99 3.59 6.88 12.30 SODIUM~ AND POTASSIUM IN PRODUCT NanSO4 KZSO4 Moisture Per cent Per cent Per cent 1.6 97.4 1.0 I i Sodium by difference.
..
...............
S U MM A R Y
A small, inexpensive ash-leaching plant is described in which the principle of countercurrent lixiviation is applied, with certain resulting advantages: I-Minimum initial expense and low upkeep. 2-Low operating cost. The leach liquor requires no concentration before causticization and the caustic sludge requires no separate lixiviation. 3-High efficiency. Recovery is 99 per cent or better. 4-Rapid manipulation. Each column furnishes a spent charge and a unit of full-strength leach liquor every four hours. MISSOURISCHOOL OF MINES ROLLA,MISSOURI
ANTIMONY SULFIDE AS A CONSTITUENT IN MILITARY AND SPORTING ARMS PRIMERS' By ALLERTON S. C U S H M A N ~ Received March 29, 1918
Toward the end of the year 1916 and throughout 1917, the production of military ammunition for all arms began t o be tremendously speeded up in the United States. At the same time, the overseas commerce of the world was interfered with by trade conditions incident t o the war and shortage of ships. The result of this combination of circumstances produced a very unusual condition with regard t o the chemical constituents used the world over in the manufacture of military primers of all kinds. For years past tersulfide of antimony has been used in almost every type of primer and is considered a necessary ingredient thereof, although the percentage quantity used in various formulas varies within wide ranges. The principal sources of antimony tersulfide for this purpose are the crude stibnite ores which are found native in many parts of the world, including England, Canada: United States and Alaska. Nevertheless, the principal supply of tersulfide of antimony as far as the United States is concerned is from Japan and China and a t the present time principally from China. It is probable t h a t the segregation of this business into the hands of the nations of the Orient is largely due t o cheap labor, so t h a t if on account of any condition incident t o the war it became difficult or impossible t o import antimony sulfide from overseas, the result would be t h a t the price of the crude materials would advance. Native antimony sulfide could then be produced in sufficient 1
2
Published by permission of the Chief of Ordnance. Lieutenaht-Colonel, Ordnance Department, N. A .
Vol.
IO,
No. 5.
quantity and of a sufficiently satisfactory grade t o assure the country a n adequate native supply. Antimony occurs in nature chiefly as the tersulfide (Sb&) in the mineral stibnite and t o a smaller extent in combination with other metallic sulfides under a variety of names, such as bournonite, pyrargyrite, kermesite, etc. For the purpose of this paper, however, i t will be sufficient t o confine the discussion t o t h e consideration of the more or less pure stibnite ores t h a t occur in nature. A s these ores are rarely free from a siliceous gangue, it is necessary in the preparation of the material for use as a primer constituent t o melt or liquate the oreout of contact with the air. Stibnite, when pure, melts a t approximately j j o o C . In the process of melting, a certain amount of metallic antimony is separated from the melt and goes to the bottom, while, on the other hand, the siliceous gangue impurities rise t o the top. On cooling down the melt, therefore, the intermediate layer represents the liquated antimony sulfide which should be carefully separated from the other two layers and represents the raw material of the antimony sulfide used as a primer constituent. If during the process of melting down, the antimony sulfide comes into contact with oxygen of the air, i t is t o a greater or less extent oxidized and the material is not pure sulfide of antimony but contains an indefinite proportion of oxide, and possibly some in the form of oxysulfide intimately associated with the tersulfide which has not been oxidized or burned. The work of liquating t h e crude ores is principally done in China and Japan before the material is imported into the United States; with the result t h a t heretofore there has been b u t little control of this process and the antimony sulfide available in the open market has shown a wide variation in its chemical analysis and therefore in its quality. Textbook and periodical literature on the subject of specification of antimony sulfide as a constituent of primer mixtures is for the most part meager and often misleading and inaccurate, It is usually the custom t o direct t h a t the purity of the antimony sulfide in quektion shall be determined by analyzing the material for antimony by any of the well-known volumetric methods and then calculating the percentage of antimony t o the basis of the tersulfide (Sb&) which in a sample of pure stibnite should figure out very close t o 100 per cent. A number of chemists have become aware of the fact t h a t analyses and calculations made on this basis very frequently led t o results running over I O O per cent, which was assumed t o be due t o the fact t h a t some slight amount of free antimony accompanied the antimony sulfide. On the other hand, when calculations were made on the same basis of analyses and came out less t h a n I O O per cent, it was considered t h a t this showed an unsatisfactory grade of purity in the material. The fact t h a t the antimony determination is easily and quickly made, while the determination of sulfur in the material has been considered a difficult and unsatisfactory determination, has probably been the principal cause of this state of affairs.
May, 1918
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
The assumption has always been made by explosives chemists t h a t the material required for making efficient primers was pure tersulfide of antimony (stibnite) of as high a degree of purity as the market or methods of treatment of the original ores would make i t possible t o obtain. It has a t no time, as far as the writer of this paper is concerned, been suspected t h a t very possibly, if I O O per cent pure stibnite was available on a large scale, i t would not lend itself so efficiently t o the manufacture of high quality primers as does the ordinary liquated crude antimony sulfide which can be made practically available in large commercial quantities. I n fact, the whole question as t o the proper grade or condition of the antimony sulfide for the commercial production of high-grade primers has been so obscured by theory, opinion, rumor and loose statement t h a t it has been almost impossible for a worker in this field t o make any definite decision with regard t o this important subject. The primer, as its name implies, is expected t o initiate every explosion which takes place from the first burning of the propellant powder t o the final explosion of the shell, if such explosion is designed t o take place, when i t arrives a t the final place where detonation is required. It is therefore quite apparent t h a t the success of ammunition, and very often the final decision in war, must hang directly upon the efficient and proper functioning of the greatest possible number of all primers loaded. It is apparent t h a t the efficient functioning depends upon the proper selection of the constituent materials which enter into the priming mixture. There are, of course, a number of different types of primers and quite a wide variety of selection is made in different types of constituent chemicals, but since antimony sulfide is common t o almost all primers, for the purpose of this paper, no discussion of the other chemicals aside from antimony will be included. As far as antimony sulfide is concerned, i t can be reiterated t h a t the book references as t o the quality which should be sought are generally vague and unauthoritative. As a n example of this, i t will be sufficient t o cite the paragraph with which antimony sulfide is dismissed in the latest (1917) edition of Marshall's compendium on "Explosives, Properties and Tests,',' Volume 11, page 686: "This material is found native in England and other countries, it has a density of 4 . 6 3 and the pure substance melts at 5.55". At high temperatures it is volatile. The crude ore is refined by melting out the antimony sulfide, which then forms bluish gray lumps with a metallic luster and very brittle. I t is also produced artificially, but in Germany it is forbidden to use in explosives the artificial product, or such as contains iron. It is absolutely essential that it should be free from sulfuric acid, as this has a very deleterious effect on the stability of explosive mixtures containing a sulfide and a chlorate, such as cap compositions. When treated with aqua regia it should not leave a residue of more than 0 . 5 per cent. It should be examined to see that it is not adulterated with sulfide of lead or iron, and that it contains little arsenic. The value of the substance as a constituent of cap compositions seems to be due largely to its hardness and crystalline form, which render the compositions sensitive to blows and friction."
It will be noted t h a t the above paragraph gives very little information on the subject. The impression is given by the paragraph t h a t what is wanted is practically pure stibnite and, above all, t h a t i t should be free from sulfides of lead or iron and contain little
377
arsenic. I t further states t h a t the residue after treatment with aqua regia should not amount t o more than 0 .5 per cent. It will be the object of this paper t o show, as the result of a n extended and exhaustive research, t h a t none of the statements made in the abovementioned paragraph are based upon facts and t h a t they are mainly incorrect. As a matter of fact, i t may fairly be doubted whether any antimony sulfide used throughout the world in primer compositions a t present would be found t o leave a residue after treatment with aqua regia of not more than 0.5 per cent. I n fact i t would probably be impossible t o obtain such material in large commercial quantities, even if such a specification were essential. As a matter of fact, very good primers can be made with antimony sulfide containing u p t o 5 per cent residue insoluble in aqua regia. This residue, as would be expected, is mainly siliceous and the objection t o its presence can only be because, just t o the extent that it is present, it reduces the proportionate quantity of active sulfide of antimony. Moreover, high percentages of silica in the form of grit will wear away the charging tools which are part of the machines which are used in the manufacture of the finished primer. Certain primer mixtures are loaded dry, in which case the presence of any considerable amount of gritty silica will lead t o explosions in the presses, which, though not of a very serious nature and which are always expected t o occur t o a certain extent, are, of course, not desirable. For this reason i t is well t o select antimony sulfide with as low silica content as possible, but very excellent primers can be manufactured if properly compounded, in which the silica content of the sulfide runs from 2 per cent t o 3 per cent, which is within the bounds of practical accomplishment on a large commercial scale of operation. The statement t h a t the antimony sulfide should be free from sulfides of lead or iron, can be shown t o be a totally unnecessary specification, for this paper will set forth the results of investigations in which sulfide of lead and iron have been entirely substituted for antimony sulfide, with the results t h a t very excellent primers have been made from these materials. It is not logical to assume t h a t if excellent primers can be made with these sulfides, with the exclusion of antimony, small quantities of such sulfides existing as an impurity in the antimony sulfide would necessarily be deleterious. As a matter of fact, such textbook statements naturally increase the anxieties and difficulties which press upon the explosives chemist in the proper specification of constituent materials for primer mixtures. This subject will be returned t o in detail in a later portion of this paper. I t should suffice, however, a t this place, t o point out t h a t if authors preparing textbooks on explosives would be careful t o include only such information as is based upon authoritative evidence with citations t o the literature, the whole question of production of ammunition on the sudden large scale demanded by modern warfare would be made easier for all concerned in its manufacture.
378
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Probably the most important point, and one t h a t has been most discussed and debated with reference t o the proper grade of antimony sulfide for use in primers, has reference t o its degree of purity a s governed b y the amount of actual antimony tersulfide present, irrespective of outside impurities. By this is meant the degree of oxidation of the sulfide which has taken place in the process of liquation. It has been this point which has led t o quite extreme differences of opinion among explosives chemists and on which but little evidence and data were available until the investigation set forth in this paper had been concluded. Up t o October 1917 specifications for ground antimony sulfide as used a t Frankford Arsenal prescribed t h a t the ground material shall on analysis show a percentage of antimony sulfide not lower t h a n 98 per cent of Sb&. I n the light of present knowledge, this specification was irrational and impossible. The specification was based on the percentage of antimony found and did not take into consideration the percentage of sulfur present or rather the amount of oxide or of sulfide t h a t had been formed in the process of liquation. Liquated Chinese antimony sulfide comes into the market under the trade names of ‘(crude” or “needle” antimony. As the earthenware pot furnaces in which the liquating is carried out are presumably never quite air-tight, the product is t o a greater or less extent oxidized and contains oxygen in the form of oxide and oxysulfide. Numerous careful analyses of the antimony, sulfur and oxygen content of various Samples of “needle antimony” made a t Frankford Arsenal show t h a t this material as prepared for primer manufacture throughout the United States and Canada approximates around 80 per cent SbzSa, 18 per cent Sb203,and 2 per cent aqua regia insoluble. Just how the oxide is associated with the sulfide in the needleshaped crystals of liquated antimony sulfide must remain for the present a matter of conjecture. It is apparent t h a t there may be several possibilities: the oxides may be present as oxysulfide or oxide either in the form of a solid solution (eutectic) or as mixed crystals. A careful microscopic research would determine this point if it were considered worth while. I n the meantime, however, it is known t h a t if powdered “needle antimony” is boiled or washed in a ten per cent solution of tartaric acid and immediately washed with water and dried, the product will analyze with a higher percentage of antimony sulfide. Tartaric acid treatment has therefore been used as a method of analysis for determining the amount of oxide present in a given sample. As a method of analysis, however, the tartaric acid extraction is extremely crude and inaccurate, for not only is antimonious oxide in a crystalline form difficultly soluble in the acid, b u t also t h e crystalline sulfide is not entirely insoluble. Manifestly, the only correct method of determining the percentage present is by igniting the sample in a combustion tube in a stream of pure, dry hydrogen sulfide a n d collecting and weighing the water formed. It is evident, however, t h a t both the tartaric acid
Vol.
IO,
No. 5
and the ignition in hydrogen sulfide treatments furnish a method which might be adapted t o the commercial scale of operation if i t were desirable or necessary t o attempt t o increase the percentage of actual Sb& present. I n fact, treatment with tartaric acid has already been recommended by several workers, who are interested in the manufacture and inspection of primers, as a method of washing and purifying ground “needle antimony” intended for use in the manufacture of military primers. T h a t such a method of treatment would involve not only a n additional amount of troublesome and expensive work, b u t also grave danger, cannot be denied. I n a program of manufacture which comprehends the production of millions of primers per day, such a treatment of the ground antimony sulfide for use in the mixtures would be a serious consideration t o any manufacturer, whereas, if all of the reacting tartaric acid is not perfectly and completely washed o u t of the material before re-drying, a new danger is injected into a n already difficult and dangerous process of manufacture. If, however, i t could be proved necessary t o add this additional treatment t o t h e preparation of high-grade antimony sulfide for the purpose intended, neither t h e expense, time nor danger would constitute a sufficient reason for not carrying out the process. T h e question is, is i t necessary a n d t o what extent? Will experimental d a t a collected b y a n exhaustive investigation serve t o show t h a t better primers can be manufactured with antimony so treated t h a n with the commercial grades of Chinese “needle antimony” which are a t the present time available for t h e purpose? It was with these considerations in mind t h a t the investigation which is the subject of this paper was undertaken and the results of which investigation will now be set forth. It is obvious t h a t such a n investigation must not confine itself merely t o t h e problems of analytical chemistry involved, but must also carry the problem into the actual manufacture of military primers and t o the subsequent problem of drying, loading a n d proving. This can be carried out efficiently only when the chemical laboratory is working in t h e closest codrdination and codperation with t h e small arms manufacturing department and with the proof house where the actual ballistic records of different experimental lots of primers can be put t o t h e last and final test in all types of small arms, including t h e 0 . 4 5 caliber pistol and revolver and t h e 0.30 caliber for rifles and machine guns of all types a t present used in the service. ANALYSIS
It has already been stated t h a t it h a s been hitherto the common practice among most of the purveyors and consumers of antimony sulfide t o specify and grade the material on the basis of purity calculated from the percentage of antimony found on chemical analysis, instead of from the percentage of sulfur. It is now known t h a t this practice was wrong and has led t o great confusion of thought and opinion
T H E JOURNAL‘OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
May, 1918
As a n instance of this, t h e following is quoted from t h e announcement of a leading dealer in ground antimony sulfide: “Antimony sulfide (needle). Guaranteed metallic antimony minimum 70 per centequivalent to about 98 per cent sulfide. Lump or 150 mesh.”
As a matter of fact, this particular brand, based on the sulfur content of 2 2 . 3 6 per cent, really contained about 80 per cent Sb2S8and 18 t o 19 per cent Sbz03. The chemical methods which have been used in the determination of sulfur, may be roughly divided into ( I ) fusion, ( 2 ) evolution, ( 3 ) wet oxidation, ( 4 ) electrolytic. The most consistent and accurate results are obtained by digestion of the finely ground sample in bromine and carbon tetrachloride with subsequent dilution, filtration and precipitation of barium sulfate. Consistent results have also been obtained with bromine and acetic acid as the oxidizing medium. Designating these methods as “A” and “B,”respectively, t h e following check results have been obtained in the course of this investigation. All other methods for the determination of sulfur have been rejected as leading t o inconsistent results. The samples included in the table were as follows: F. A. 42’and F. A. 88, representing material purchased to a specification very similar, except as t o granulation, t o the dealer’s grade quoted above. It may be stated a t this place t h a t many millions of eminently satisfactory primers have been manufactured from the lot of antimony sulfide represented by these samples. There have also been manufactured many millions of primers from this same lot t h a t were defective. I n the defective ammunition, however, the granulation of the antimony sulfide was not correct and other subsidiary causes of the defects were discovered. The sample marked C. L. was a picked sample of Chinese lump from a consignment recently imported. The sample J . S. was pure stibnite from the Ichino Kawa Mine, Iyo, Japan, where magnificent groups of brilliant crystals up t o 20 inches in length of very high purity are found. The results of the analytical work are given in Table I :
Sample F. A. 4 2 . .
TABLEI Method A Sulfur found Per cent 22.36 22.54 22.08 22.53 22.50 26.34 26.42 28.52
.............
F. A. 8 8 . .
.............
Method B Acid Insoluble Sulfur found Per cent SiOz, etc. Per cent 22.37 2.5
C . L ..................
22.69 22.75 26.42
0.2
...................
28.50
None
J. S
2.5
Calculating the percentage of SbzS, present in F. A. 4 2 and F. A. 88 from the sulfur content found, we get 78.4 and 7 9 . I per cent, respectively, instead of approximately 98 per cent calculated from the antimony content. The above-described work establishes the fact t h a t granulated Chinese “needle antimony,” such as has been in common usage for many years in munition
379
manufacture, does not run better than approximately 80 per cent actual Sb&. The following questions immediately suggest themselves: I-Would it be of material advantage t o the end in view t o use antimony sulfide of a higher degree of purity? a-Would i t be practical and worth while to attempt t o treat the 80 per cent sulfide in order to increase its purity and if so, what impurities are the ones t o be considered harmful? I n order t o get light on these questions, the investigation was directed t o the study of treating ground samples of antimony sulfide with tartaric acid solutions of varying strength under varying conditions. After numerous experiments i t was found t h a t a IO per cent solution of tartaric acid was as effective for the purpose in view as stronger solutions and, further, t h a t in order to get the maximum results without producing decomposition of the antimony sulfide itself, boiling for 3 0 min. is required. If cold digestion is resorted to, 5 or 6 days are required to approximate the maximum extraction of oxide. On the other hand, the purest Japanese sulfide free from oxide yields I per cent extract on 3 0 mins. boiling and 4 per cent on 3 hrs. boiling in I O per cent acid when 150-mesh samples are being used. I n the same time F. A. 88 antimony sulfide yielded 16 per cent and selected Chinese lump 6 per cent extract in the g o-min. test. The above work has shown very clearly t h a t while treatment with tartaric acid does remove a considerable portion of oxide t h a t is present as oxide, i t does not remove oxysulfide and, moreover, i t is shown t h a t even the purest antimony sulfide is t o some extent decomposed by the acid. It is, of course, obvious t h a t while the oxide impurity is being lowered, all acid-insoluble impurities present, such as silica, are being increased. The danger of the introduction of tartrates into the final product is objectionable. The conclusion drawn by the author as the result of this part of t h e inqestigation is t h a t tartaric acid treatment of antimony sulfide intended for use in military primers should not be permitted. It is apparent from what has been stated that commercial liquated antimony sulfide is never a pure product containing antimony and sulfur in the proportions of Sb&, but is always contaminated with oxygen, which it absorbs while in the molten state. Munitions laboratories have heretofore generally based their specifications on purity calculated from the amount of SbzS3 figured from the percentage antimony found, instead of from the percentage of sulfur. This practice is shown t o be wrong. As a matter of fact, most commercial needle antimony sulfide will run from about 80 t o 8 5 per cent actual Sbz& and from material obtained t o 80 per cent specification very excellent primers can be manufactured as will be demonstratad in the succeeding pages. The correct analyses of a number of samples of antimony sulfide in actual use by manufacturers of military primers are given in Table 11:
380
T H E J O U R N A L OF I N D U S T R I A L A N D EiVGINEERING C H E M I S T R Y
TABLE 11-ANALYSES OB ANTIMONY TERSULFIDE(NEEDLE ANTIMONY) Anti- Sul- S as Oxymany fur SbPSslnsol.gen Iron Lead Arsenic
Per cent F. A. 88................. 69.6 F . A . 4 2 . . . . . . . . . . . . . . . . .70.0 Chinese L u m p . . . . . . . . . . . 71.3 Manufacturer A , . . . . . . . . . 69.0 Manufacturer B . . 70.0 Manufacturer C . . 71.3 Manufacturer . . 71.8 Dealer B . . . . 71.4
Per cent 22.6 22.4 26.4 21.3 23.2 22.0
Per cent 79.1 78.4 92.4 74.6 81.3 76.9
Per Per cent cent 2.8 4.6 2.1 0.21 5.5 2.4 1.2 1.3 24.5 75.8 1 . 6 2.2 2 8 . 5 99.9 0.00
Per cent 0.06 0.06 0.04
Per cent Trace Trace Trace
Per cent None None None
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . .. .. .. .. .. .. .. .. ..
The method of determining sulfur adopted by the Frankford Arsenal Laboratory as giving fairly quick and accurate results is as follows: Treat 0 . 5 g. of the powdered sample in a covered No. 2 beaker or small flask with a mixture of 1 cc. HzO, 9 cc. glacial acetic and 6 cc. liquid bromine a t room temperature; let stand overnjght. In the morning add 20 cc. conc. HC1 and warm gently for half a n hour. Remove the cover and evaporate to “soft dryness” on steam bath. Take u p with 10 cc. conc. HCI and a little water. Add 2 g. of tartaric acid and dilute t o 150 cc. with hot water. T o t h e warm solution add 0 . 5 g . powdered aluminum, a little a t a time, until the antimony is precipitated a s metal. Filter a t once a n d wash the precipitate with hot water. Allow t h e filtrate t o cool. Dilute t o about 600 cc. a n d precipitate BaSOa by adding 25 cc. of a 10 per cent solution of BaClz from a burette.
The method used for the determination mony in needle antimony sulfide is as follows:
Of
anti-
Weigh accurately 0 . 3 g. of sample and brush carefully into a n 800 cc. Erlenmeyer. Add 35 cc. HC1 (sp. gr. 1.19) and let stand in the cold for thirty (30) min., after which t h e hydrogen sulfide is expelled by heating on the water bath. Then a d d 20 cc. conc. HCl, 20 cc. conc. HzS04 and 100 cc. water, Boil 15 t o 20 min. t o drive off all SO2 and HpS; dilute to about 600 cc. a n d cork u p with a connection to a bottle of NazCOs and cool under t a p quickly. Titrate a t once t o first pink with N/10 KMnOi standardized against Bureau of Standards’ sodium oxalate, prepared according t o Sorensen, or run a blank against C. P. metallic antimony.
The method selected for. the determination of lead and iron is as follows: Weigh 5 g. of sample into a small beaker and treat with 60 cc. HNOa (sp. gr. 1.4). When SbpSs is completely decomposed, take down t o moist dryness; add 5 CC. conc. “OX, dilute t o 100 cc. and filter through a double filter (595 S. S.). Wash free from acid and determine lead in t h e filtrate by adding 10 cc. HpSOa (1 : 1). Evaporate to dense white fumes on any suitable hot plate; COOI,add water and filter the PbSOr on a prepared Gooch crucible. Washin diluted &So4 (1-loo), once in alcohol, and dry at 250’ C. for one hour. Cool and weigh. PbSOc X 0.6831 = Pb. Transfer the lead filtrate t o a 600 cc. beaker, boil off alcohol; then add 3 g . of ammonium chloride and heat t h e solution t o boiling. Precipitate t h e iron with a slight excess of ammonium hydroxide. Cover a n d boil for 5 min. Remove the cover and let settle for 20 min., filter on a fast running paper and wash well with diluted ammonia (1-5). Wash well Redissolve the iron with 15 CC. HCl (I-I), three times with hot water. using this acid t o rinse t h e beaker. Add 2 g. of NHiCl and a few drops of Reprecipitate the iron and filter. Wash three times in diluted am“03. monia, twice with hot water. Dissolve t h e iron off the paper with 20 CC. of H ~ S O(1-4) ~ into a small Erlenmeyer. Add 1 g. of 20-mesh zinc, warm on a hot plate and when dissolved titrate with N/30 KMnOi t o a permanent
pink.
The method used for determining oxygen in needle antimony sulfide is as follows: One gram of t h e finely powdered sample is weighed into a porcelain boat and heated in a glass combustion tube in a stream of pure, dry hydrogen sulfide. After all air has been displaced, the combustion t u b e is heated very gently a t first and finally t o t h e fusion point of the sulfide, about 550’ C. Care must be taken not t o allow the temperature t o rise much above t h e melting. . point, as s b 2 s Band Sbz03 volatilize a t higher temperatures. The water formed in the reaction is collected in a n absorption t u b e in t h e usual manner and after displacing the hydrogen sulfide with dry air, is weighed. Blanks should be run on pure stibnite t o calibrate t h e apparatus.
The determination of aqua regia insoluble impurities in antimony sulfide is determined as follows: Weigh 5 g . of sample into a 400 cc. beaker and treat with 200 cc. aqua regia (1 part “ 0 8 , 3 parts HCl). Keep on hot plate for one-half hour to comDlete solution and exDulsion of all H2S. Filter on well-packed asbestos Gooch. Wash free from acid and once with alcohol. Dry a t 250’ C . a n d finally ignite t o volatilize any separated sulfur. Cool, weigh and report as insoluble in aqua regia.
Vol.
IO,
No. 5
BALLISTIC T E S T S
The quality and ballistic accuracy of small arms ammunition depends upon a number of factors. If i t be assumed t h a t the powder, cases and bullets are 0. K. in a given lot, erratic ballistic results are invariably ascribed t o the primers. The primer is unquestionably the heart of t h e cartridge and is depended. on t o initiate the functioning of each and every shot. I n its t u r n the functioning of the primer per se involves a number of factors, each one of which in an ideal primer (if such a thing indeed existed) must not only be right in itself, b u t must codrdinate with all the others in just the right way. Small arms primers are made of an intimate mixture of reacting chemicals, which mixture is then machine-Pressed into small brass or gilding metal cups foiled with a paper disc, a small brass anvil inserted and the primers dried, after which they are ready for the loading operations. The chemical mixture or composition varies widely in the different formulas developed by the separate munition manufacturers and governments. It is not the intention of this paper t o enter into a discussion of the comparative defects or merits of different wellknown primer mixtures, many Of which have been patented. I t . may be stated briefly, however, t h a t primer compositions divide roughly into two typesdetonating and burning* In the detonating type mercury fulminate, lead, azide or Some similar substance which can easily be detonated by a percussive blow is made the base of the composition. I n the burning type we have t o consider more or less wellbalanced mixtures of fuel and oxygen-carrying constituents. For the Oxygen carriers the dependence is potassium chlorate with sometimes a n additional small quantity of barium or some other nitrate. The fuels selected are Usually sulfur Or Some sulfide or sulfa salt with or without the addition of carbon or carbonaceous material. The one striking thing about primer in general throughout the world is t h a t they almost contain Some proportion Of antimony sulfide regardless of whether they are representative of the detonating or burning type. The author is. with Only One modern primer which was made u p without antimony sulfide, but and it is understood t h a t this has not been a the manufacturers have recently modified it by a n addition of antimony sulfide to the formula. Since antimony sulfide is so generally admitted t o be a necessary ingredient Of good primer compositions, the question a t once suggests itself as t o just what r y e it plays in t h e functioning? on this subject there has been much difference of opinion on t h e part of various authorities. It must be very generally conceded t h a t in order t o burn the powder properly, a primer should function a t the instant i t receives the percussive blow of t h e firing pin without showing delay action leading t o “hangfires.” I n particular, it a good show a high heat Of deoth of nenetration. not too violent explosion and large gas broduction ‘of such it natureas to produce a long flash of flame. Above all, it must possess -L
May, 1918
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
properties which will prevent its deterioration in storage and in service and must be of a sufficient but not too high sensitiveness. Now i t is possible t h a t the presence of antimony sulfide affects all of these desired qualities, although not all t o the same degree. There are in addition t o the above, three other possible functions of antimony sulfide in primer compositions. I-The hard, smooth grain of the needle crystals may act the part of a friction agent similar t o t h a t produced in certain primer compositions by the introduction of powdered glass. 2-The needle grains may hold apart or insulate the more reactive chemical agents in the mixturz and thereby control sensitiveness and reduce tendency t o deterioration. 3-The needle .antimony may act in part or as a whole as a contact or catalytic agent and modify the explosive reactions. It may be admitted t h a t for one or all of these reasons antimony sulfide or its equivalent is a necessary constituent of all primer mixtures. Since it is known that the present source of supply of needle antlmony is from China and Japan and since i t is not without the bounds of possibility t h a t a t some time or other importations might be interfered with, i t is important t o determine whether antimony sulfide of a grade of purity which could be produced in this country would be equally as effective as the imported material and also whether other domestic mineral sulfides which occur in sufficient abundance could be substituted in a n emergency. The answers t o these questions can be obtained only by making up lots of experimental primers, loading them into ammunition and making the usual ballistic tests for muzzle velocities, barrel pressures, sensitiveness and freedom from misfires and hangfires. It i s not nccessary in this paper t o discuss in detail all the required ballistic specifications t h a t finished small arms ammunition has t o meet, but the following requirements are quoted from Ordnaizce Pamfihlef No. 544: “On inspection and tests of finished cartridges, the standard velocity at 78 feet is 2640 foot seconds. The mean velocity must not vary from these standards by more than 30 f. s (2610 f . s. - 2670 f . s.) in the model of 1903 rifle. The mean variation in velocity must not exceed 20 f . s. in the model of 1903 rifle. “The maximum pressure must not exceed 52,000 lbs. per square inch in the model of 1903 rifle.”
It will be seen from the above t h a t if the powder cases and bullets are quite right, the primer must burn the standard charge of powder in such a manner as to produce a muzzle velocity of about 2 6 4 0 f t . seconds a t a pressure not t o exceed j 2 , 0 0 0 lbs. per sq. in. If a primer is weak from any cause, pressure a n d velocity will run low. A good primer will tend toward maximum velocities with minimum pressures. If pressures run high for norma1 velocity, discussion is in order t o determine whether the powder or the primer is a t fault. I t is apparent, therefore, t h a t a primer can be too strong and t h a t the narrow limits of satisfactory functioning present the most perplexing problems t o the primer manufacturer.
381
One method by which the manufacturer seeks to gain information and control of his production is by means of the drop test by which samples usually about one-half per cent of output are shot. All misfires must be accounted for or the lot of primers represented by the sample rejected and destroyed. Perhaps the greatest value of the drop test lies in the fact t h a t in expert hands it can be used t o measure the comparative sensitiveness of different lots and types of primers and it serves t o keep the character of the functioning continually under observation. When improperly used and interpreted there is no test more confusing or misleading. Unfortunately, the type and arrangement of drop testing machines has not been standardized. Each manufacturer pursues his own method of testing and there are many conflicting opinions in regard t o specifications for sensitiveness. The object of this paper is t o set forth the results of tests made t o determine t o what extent the degree of purity of the antimony sulfide used in the primer composition effects the sensitiveness of the finished primers. All other variables such as the granulation, or grain size of the antimony, were kept constant and based on the standard practice used by the author a t Frankford Arsenal in the manufacture of the service F. A. 88 primer. The sensitiveness test selected for this investigation was the minimum height of fall of a 3-02. weight with firing pin attached t h a t would just begin to show misfires. The primers under test were inserted with all necessary precaution in a steel die. The regular F. A. 88 primer was made the standard for comparison. The composition of the F. A. 88 primer will not be given in this paper, but it may be stated t h a t it is of the non-fulminate or burning type and t h a t i t is made so as t o contain 17 per cent of specially grained needle antimony sulfide. The analysis of the needle antimony has already been given in Table I1 and i t will be noted t h a t it is not by any means pure, but contains about 18 per cent of oxide. The fact t h a t F. A. 88 is a highly efficient and satisfactory primer under service conditions, proves conclusively t h a t needle antimony containing about 80 per cent actual Sb2S3is sufficiently pure for primer manufacture. The first question t h a t naturally arose was: What results would be obtained if the F. A. 88 primer was made up using pure stibnite in Che place of crude needle antimony? Through the cooperation of the National Museum, a sample of pure crystalline antimony sulfide (stibnite) was made available. The results of the sensitiveness test were as follows: TABLE I11 F. A. 88 with pure stibnite 3-02,weight 3-02, weight 100 0. K. at 19.5 in. 100 0. K. at 19.5 in. 100 0. K. at 19.0 in. 100 0. K. at 19.0 in. 100 0. K. at 1 8 . 5 in. 97 0. K. 3 misfires at 18.5 in. 96 0. K. 4 misfires a t 18.0 in.
F. A. 88 regular
The above results show t h a t pure stibnite increased the sensitiveness about in. for the 3-oz. weight. Carefully calibrated indentation tests have shown t h a t a weak-spring gun with 14-lb. pull corresponds t o a 22-in. drop, so it is shown t h a t the slight increase
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
382
in sensitiveness gained b y the use of pure stibnite would not justify the expense of obtaining it on a commercial scale. F I R S T EXPERIMENT-The ballistic proofing of finished ammunition is the best test of the primer, and therefore experimental lots of hand-loaded ammunition were made up and fired for pressure and velocity in the usual way. The results of the competitive firings between F. A. 88 (regular) and F. A. 88 (pure stibnite) are as follows: TABLEIV F . A. 88 (Regular) F . A. 88 (Pure Stibnite) Powder charge in each shot 4 8 . 8 grains SHOT Velocity Pressure SHOT Velocity Pressure No. Ft.-Sees. Lbs. No. Ft.-Secs. Lbs. 1 2649 48700 48200 2 2660 47750 3 2681 48450 4 2656 45900 5 2646 46650 6 2665 46150 7 2646 47700 8 2656 46650 9 2646 47150 10 2644
........... ........... ........... ........... ........... ........... ........... ...........
........... ........... -MEAN....... 2655
-
47155 Powder, primers, bullets, cases, 0. K .
2649
47330
An examination of the above able will convince anyone familiar with the ballistics of small arms ammunition t h a t as far as these firings were concerned, there is nothing t o choose as between the primers made with needle antimony sulfide of about 80 per cent purity (SbzSa) and those made with stibnite I O O per cent purity (SbzSS). S E C O N D EXPERIMENT-starting with pure I O 0 per cent stibnite, it was decided t o t r y the effect of the deliberate addition of 18 per cent of soft powdered yellow antimonous oxide thoroughly mixed with the granulated stibnite. It was further decided t o make up another lot with the needle antimony sulfide which had been purified with tartaric as described in a previous paragraph. The results of the ballistic tests are given in Table V and are comparable with those given in Table IV. TABLEV F. A. 88-With pure antimony F. A. 88-With antimony sulfide treated with tartaric acid sulfide plus 18 per cent SbzOs Standard powder charge 48.8 grains SHOT Velocity Pressure SHOT Velocity Pressure No. Ft.-Sew. Lbs. No. Ft.-Secs Lbs. 46500 1 2722 48200 2 2714 46400 2701 3 47900 4 2698 49450 5 2689 48500 6 2694 47150 7 2664 47900 8 2709 47050 2667 9 47100 10 2694
........... ........... ........... ........... ........... ........... ........... ........... ........... ........... M E A N . ...... 2695
-
47865 Powder, primers, bullets, cases, 0. R.
_ .
2697
47615
When we compare t h e above results with each other and with the results given in Table IV, there is little t o choose between them. All four series are ballistically satisfactory. On the drop test, all primers shot 0. K. a t 2 1 in. It is very clearly indicated t h a t the presence of 18 per cent of antimonous oxide, whether it occurs as a natural impurity or as a deliberate introduction with pure antimony sulfide, need not be a source of anxiety in the manufacture of military primers when a good mixture is being used. THIRD E x P E R I M E N T - I t will be remembered t h a t in a n earlier paragraph of this report a statement was
Vol.
IO,
No. 5
quoted from Marshall's book on explosives1 t o the effect t h a t sulfides of lead a n d iron were objectionable in cap primer compositions. The statement was not qualified as relating t o the fulminate type exclusively, and it was felt t h a t a mere statement unsupported b y data was unconvincing. The easiest way t o get a t the desired information seemed t o be t o make up lots of F. A. 88 primers in which the antimony sulfide was entirely replaced in one lot by crystalline lead sulfide (galena) and in another b y crystalline iron sulfide (pyrite). Fairly pure samples of these two minerals were obtained, granulated and sieved t o t h e standard grain of the antimony sulfide ordinarily used in the F. A. 88 primer. The results obtained were somewhat surprising as the author had thought t h a t the primers would prove themselves t o be defective and show tendencies t o being either too sensitive or not sensitive enough. Why antimony sulfide was originally selected by explosives chemists as the only possible sulfide for use in primer compositions and why t h e impression prevails t h a t the antimony sulfide used must be of very high purity is not explained by the results of this investigation. TABLEV I F . A . 88-Made with lead sulfide F. A. 88-Made with iron sulfide (galena) instead of antimony sulfide (pyrite) instead of antimony sulfide Standard powder charge 4 8 . 8 grains SHOT Velocity Pressure SHOT Velocity Pressure No. Ft.-Secs. Lbs No. Ft.-Secs Lbs. 1 2697 2700 2 2713 3. 2715 4. 2688 5. 2723 6. 2715 7 2692 8. 2697 9... 2700 10.
........... ........... .......... .......... .......... .......... ...........
.......... ........ .......... MEAN....... 2704
-
47545 Powder, primers, bullets, cases, 0. K.
2704
47840
The drop test sensitiveness of the foregoing lots of primers was satisfactory for the lead sulfide a t 2 1 in. The iron sulfide was a trifle more insensitive a t ~ 2 1 /in., ~ whereas 2 2 in. is the calibration factor corresponding t o the 14-lb. weak-spring gun. AS far as shooting quality is concerned, t h e iron sulfide and lead sulfide primers showed up in these tests slightly superior t o t h e regular F. A. 88 primer. Retests were made in nearly all series of shots given in the above tables, b u t as essential checks were obtained in all cases, for the sake of brevity, only the first ten shots fired in each series have been tabulated. I n making up all experimental lots, the greatest care was taken in regard t o the granulation of the antimony sulfide and its substitutes. I t is well known t h a t the sensitiveness and stability of primer mixtures is affected by t h e grain of the antimony which should not be too coarse or too fine. I n all the above described work equal quantities of three sieve sizes were used. The ground material was passed through sieves so as t o divide in 100-t o 150-mesh, 150- t o zoomesh, and through the zoo-mesh. Equal quantities of each size were then weighed and the whole very intimately mixed. These precautions of even graining should always be carefully followed in carrying on 1 LOG.
cir.
May, 1918
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
comparative tests on primer mixtures of varying compositions. SUMMARY
This paper has set forth some of the results obtained in the course of a long and exhaustive research on a large number of primer compositions and forms of finished primers. Much of this work is of too confidential a nature a t the present time t o justify publication, b u t it is believed that the data as given here will be of benefit t o many workers in this field without disclosing information t h a t would be harmful. For some time past there has been some anxiety felt in regard t o adequate supplies of very pure antimony sulfide. This paper should, i t seems, serve in some measure t o allay this fear. CONCLUSIONS
I--The purity of liquated “needle antimony” should be determined from the sulfur content. The method of basing purity on the antimony content is shown t o be incorrect. 11-The method of purification of “needle” antimony which depends on treatment with tartaric acid is shown t o be unjustifiable, if not actually dangerous. 111-The methods for the complete analysis of antimony sulfide are set forth. IV-(‘Needle” antimony sulfide of an approximately 80 per cent purity, containing about 18 per cent of oxide, is shown t o be as efficient for the manufacture of primers as approximately IOO per cent stibnite.
383
V-Sulfides of lead and iron are shown t o work satisfactorily when substituted for antimony in a non-fulminate primer. VI-It is indicated from V t h a t the presence of sulfides of lead and iron existing as impurities in antimony sulfide would not be harmful, textbook statements t o the contrary notwithstanding. VII-The conclusion is drawn t h a t in case of deficient supplies of overseas antimony sulfide, domestic ores would serve every purpose and t h a t other more abundant minerals might be substituted. Further investigation as t o stability of primers made with other mineral substitutes for antimony sulfide would be desirable before attempting their use on a large scale. VIII-The fact t h a t primers made with lead sulfide (galena) and iron sulfide (pyrite) showed a higher velocity for a normal pressure than those obtained with regular antimony sulfide, is interesting and suggestive but by no means conclusive as a much more extensive experimental program would have t o be carried out before any definite conclusion could be reached. In concluding this paper the author desires t o express his great appreciation of the interested and able assistance which he obtained in carrying out the experimental part of this work from Mr. J. K. Miller and Mr. Sydney N. Greenburg, Explosives Chemists, employed a t Frankford Arsenal. PHWADELPHIA, PA.
ADDRESSES FOOD CHEMISTRY IN THE SERVICE OF HUMAN NUTRITION1 B y H. C. SHERMAN Received March 26, 1918
At the suggestion of your President I propose to speak this evening of the application of food chemistry to problems of human nutrition with special reference to the economic aspects of our present food situation, i. e., to consider how in the light of our present knowledge we can best combine adequacy of nutrition with economic use of food-remembering, too, that economic in this connection and a t this time should mean not only the wisest expenditure of money for food from the standpoint of the consumer, but also such conservation of the food resources of the entire country as shall enable us to furnish our Allies and our armies abroad with the largest possible share of those foods which are adapted to their needs and suitable for exportation. Briefly and somewhat crudely, the material requisites of an adequate diet may be summarized under five heads. It must ( I ) provide sufficient amounts of digestible organic nutrients to yield the necessary number of Calories of energy; (2) furnish proteins in ample amount and of suitable sorts; (3) supply adequate amounts and proper proportions of the ash constituents, salts or inorganic foodstuffs; (4)furnish enough of those as yet unidentified substances, the food hormones or so-called vitamines; (5) it must include a sufficient amount of material of such physical character as to ensure the proper handling of the food mass and its residue in the digestive tract. Since we are here to deal with the chemical rather than physical aspects, discussion may be limited to the first four of these requisites. Logically each of these four categories calls for subdivision. 1 Lecture delivered before the Harvey Society, Academy of Medicine, New York City, January 12, 1918.
As sources of energy the carbohydrates, fats, and proteins function interchangeably to a very large but not to an unlimited extent. If our understanding of the relation of the energy value of food to the energy requirement of the body is to be complete we must study the intermediary metabolism of each of the organic foodstuffs and its relation to the energy exchange, including the problem of its specific dynamic action. Similarly the problem of protein requirement divides itself into a group of problems having to do with the requirements of the body for each of 15’or 16 amino acids which constitute the building stones of the body tissues, and which are less widely interchangeable than are the energy values of the different foodstuffs. The ash or mineral matter comprises a t least I O chemical elements not contained in simple proteins, fats, and carbohydrates and which are not only not interchangeable but are in some cases actually antagonistic in function. Under ordinary conditions and with our usual ample use of table salt the only mineral elements requiring special consideration from the standpoint of adequacy of nutrition are phosphorus, calcium, and iron. The vitamine or hormone value of foods is due to at least two substances distinguished by McCollum as the Fat-soluble A and the Water-Soluble B. It cannot be denied that the rapid progress of our knowledge of nutrition during the past few years has tended to complicate rather than simplify our conceptions of food values and nutritive requirements. But while the problem has become more complex it also has become clearer because we now for the first time have good reason to believe that all of the substances needed for normal nutrition have been recognized and can be reckoned with even
