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should be sufficiently emulsified, in a pneumatic process, to last during the time of floating. IV-Colloids in general are harmful, owing either t o their causing too stable an emulsion, or t o their adsorption on the oil film at the bubble surface preventing mineral attachment. This is t h e action of the so-called “flotation poisons.” V-The froth formed is attributable either t o the soluble portion of the flotation mixture, which produces a variable surface tension, or to finely divided or colloidal materials. VI-Acids, alkalies and salts affect all these factors, as discussed under the several headings in the paper. VII-The electrical effects, other than the colloidal charges, are not important in flotation. VIII-The nature of the solid surface in relation t o its wetting properties has been discussed and a n explanation of the “hysteresis” of the contact angle advanced. I n the light of present knowledge, it is impossible to measure many of the forces operative in flotation, such as, for example, the interfacial tensions between solids and liquids, or t o explain the mechanism of adhesion. Such problems are, however, nearer solution, due t o the material advances made recently by Lauel a n d by Bragg and Bragg,z by which the actual arrangement of the atoms in a crystal may be determined, and also by Langmuir,a whose work on the constitution of solids and liquids, the structure of solid surfaces, and the mechanism of adsorption leads toward the solution of this problem. While the flotation of each ore still remains more or less of a problem in itself, yet a clear understanding and the proper application of the principles involved will lead t o a n earlier solution of the problem. I n conclusion, the authors wish to express their thanks to Dr. R. F. Bacon and t o Mr. E. R. Weidlein, under whose direction this research has been carried out. MELLONINSTITUTE
OF INDUSTRIAL
RESEARCH
PITTSBURGH
-~ NOTES ON THE ANALYSIS OF CAST NICHROME B y E. W. REID Received March 6, 1917
It is no new experience for chemists t o find that each alloy has its own personal equation in yielding itself t o sharp analytical results, and the remarkable group of mixtures which are coming into such general use under the popular name “Nichrome” form no exception. The following notes are submitted, not with the supposition t h a t they are the best ideally possible, but with t h e hope that they may help t o call the attention of those specially interested in related lines of research to the need of reliable methods for the analysis of this group of alloys. Site. Akad. Wh., Wien, June, 1911. Proc. Comb. Phil. Soc.. 17 (1912). 43; and treatise on “X-Rays and Crystal Structure.’’ I J . Am. Chcm. Soc., 88 (1916). 2221. 1
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Some difficulty will usually be experienced in getting the alloy into solution, and after several solubility determinations, the following method was adopted. There is always a slight residue left in the bottom of the casserole after treatment with hydrochloric and nitric acids, which appears t o be small particles of metal enclosed by gelatinous silica; hence the usual necessity of first removing the silica, and then dissolving the residue in acid, with subsequent fusion of any undissolved chromium with sodium peroxide. Cast nichrome contains approximately 58 t o 6 2 per cent of nickel, 2 3 to 2 6 per cent of iron, 8 to 14 per cent of chromium, 0.5 to 2 . o per cent of manganese, zinc and silica, 0 . 2 t o I . o per cent of carbon and sometimes a bare trace of copper. The ingredients were determined in the order given.
.
SOLUTIONS
AMMONIUM
CHLORIDE-saturated
solution.
HYDROCHLORIC ACID (SP. GR. I . 12)--8 12
cc. hydrochloric acid (sp. gr.
N/IO
POTASSIUM
Water t o
cc. water t o 40 cc.
SULFURIC ACID (SP. G R . 1 . 4 0 ) - 4 3
sulfuric acid (sp. gr.
CC.
I . 20).
1.83). PERMANGANATE-3.161
salt dissolved in water, diluted to
I
g. pure
liter.
F E R R O U S A M M O N I U M SULFATE-39. 2 g. pure salt dissolved in 500 cc. water and 50 cc. concentrated sulfuric acid added; diluted t o I liter. POTASSIUM IODIDE--:! per cent solution. POTASSIUM CYANIDE-13. j g. pure Salt and 1 5 g. Of potassium hydroxide dissolved in water, diluted t o I liter. N / I O SILVER NITRATE-8. 49 5 g. of the salt dissolved in water, diluted to I liter. TARTARIC OR CITRIC ACID---:! 5 per cent solution. BROMINE WATER-satUrated solution. POTASSIUM FERROCYANIDE-2 I . j 5 g. pure Crystallized salt dissolved in water; diluted to I liter, DIMETHYLGLYOXIME-I per cent solution. URANIUM ACETATE O R NITRATE-I5 per cent solution. “STOCK” soLuTIoN-(Described under Silicon). SILICON
Dissolve 2 . j g. of nichrome turnings in a 2 50 cc. casserole, with 20-30 cc. concentrated hydrochloric acid and 3-5 cc. concentrated nitric acid. Evaporate the solution t o dryness, take up with the above amounts of acids, again evaporate’ to dryness, and ignite t o redness for a few minutes. Take up with hydrochloric acid (sp. gr. 1 . 1 2 ) and a few drops of nitric acid; bring t o boiling; dilute with cold water and filter. Wash the residue on the filter paper thoroughly with dilute hydrochloric acid ( I : 3 ) , and finally with hot water. Carefully ignite the filter paper with its contents by means of a platinum wire over a platinum crucible, and after the ash and residue are allowed t o fall into the crucible, ignite to a high tempe;ature for ~j to 2 0 minutes, or until all the carbon of the paper is burned: cool in a desiccator and weigh. Then moisten the residue with a few drops of sulfuric acid
1
I The evaporations may be accomplished in a short time by manipulntion of the casserole over a free flame. observing the usual precautions.
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489
and heat t o boiling. Allow t h e precipitates of the iron and chromium hydroxides t o settle, decant t h e supernatant liquid through a filter paper. wash the precipitates several times by decantation with ammonium chloride and water, allowing the precipitates t o settle each time and decanting off the liquid through the filter, and finally transfer t h e precipitates to t h e filter paper and wash them thoroughly with hot water. Use t h e filtrate for the determination of zinc. IRON-Dissolve the precipitates on t h e filter paper with hydrochloric acid (sp. gr. I. I 2) allowing t h e solution t o run into the beaker in which t h e former precipitation was made, and wash t h e paper free from acid. Treat t h e solution of t h e chlorides with sodium or potassium hydroxide until strongly alkaline, add bromine water until t h e solution has a distinct yellow tinge and the ferric hydroxide has assumed its characteristic reddish brown. Boil the solution for a few minutes, dilute with water and filter. Wash t h e preNICKEL’ cipitate twice; dissolve on t h e filter paper as before; The cyanide method permits the determination of treat in t h e same manner, and filter onto t h e same paper, nickel with speed and accuracy even in t h e presence allowing the filtrate t o run into the beaker containing of iron, manganese, chromium, zinc, vanadium and t h e filtrate from t h e former precipitation; then wash tungsten; i t was adopted in preference t o t h e dimethylt h e precipitate thoroughly with hot water, dissolve glyoxime method, after repeated comparisons with on t h e filter with hydrochloric acid (sp. gr. I . 12), t h e two methods. wash the filter thoroughly with hot water, precipitate S T A N D A R D I Z A T I O N O F POTASSIUM CYANIDE-Dilute the iron with ammonium hydroxide and redissolve about 3 0 cc. of t h e potassium cyanide solution t o 2 0 0 cc., add j cc. potassium iodide solution, and titrate in sulfuric acid; finally reduce t h e iron with 5 g. of zinc ( 2 0 mesh) or pass through a Jones reducer, and with N/IOsilver nitrate until a faint opalescence is titrate with potassium permanganate. As the zinc obtained, which may be cleared u p with a small drop contains a small amount of iron, a blank determinaof potassium cyanide. The equivalent of silver nition should be made with the same amount of zinc trate, per cc. of potassium cyanide, is calculated. as t h a t used t o reduce t h e iron, and the correction T H E DETERMINATION-Dilute 2 j CC. Of t h e “Stock” made. solution t o zoo cc.; add about 2 0 cc. of t h e tartaric or cHRoMIunrl-Acidify t h e filtrate from the iron with citric acid solution, j t o I O cc. ammonium chloride, sulfuric acid (sp. gr. 1.40) and a d d a small excess of and ammonium hydroxide until slightly alkaline ; the acid. Add a solution of manganous sulfate then add j cc. of potassium iodide and 0 . j cc. of N/IO (equivalent t o 3 t o 4 g. of the solid); or, if preferred, silver nitrate, t h e latter being accurately measured dissolve 3 or 4 g. of the solid in the solution), and cool from a burette. While stirring constantly with a glass the solution. Add from a burette sufficient standard rod, add t h e standard potassium cyanide solution unferrous ammonium sulfate solution completely t o til t h e precipitate of silver iodide dissolves completely, Then add t h e silver nitrate solution until a faint reduce1the chromium present (indicated by the change in color). Titrate the excess of ferrous ammonium opalescence is obtained, which may be cleared up with sulfate with potassium permanganate t o a decided a small drop of t h e potassium cyanide. pink. If preferred, t h e Mohr salt may be added in Assuming t h a t the silver nitrate solution was ext h e solid form; this is best accomplished by placing a t h a t I cc. of potassium cyanide = N cc. actly N/Io, sufficient quantity of t h e pure salt in a small weighing of t h e silver nitrate solution, that T cc. of the potasbottle, carefully weighing t h e whole, adding t h e desium cyanide and t cc. of the silver nitrate were used in titrating A g. of the substance, and t h a t 0.002634 sired amount of the salt t o the chromium solution, is t h e silver nitrate equivalent for nickel, then t h e and reweighing t h e bottle t o determine t h e amount per cent of nickel is found b y t h e following equation: used. It is usually better t o standardize the ferrous ammonium sulfate directly against the permanganate, Per cent Nickel = ( T N - t ) 0 . 2934/d and also t o titrate a blank of the acid. The chromium I R O N AKD CHROMIU3I solution should be cooled t o 20’ C., the permanganate Transfer 50 cc. of the stock solution t o a 3 50-400 cc. added drop by drop, stirring the solution constantly, cc. of t h e or a n error may be introduced, due t o the liberation beaker, dilute t o Ijo-zoo cc., add 2-25 saturated solution of ammonium chloride, make the of chlorine. 167. 7 parts of ferrous iron are required t o reduce solution barely alkaline with ammonium hydroxide 5 2 . I parts of Cr in chromic acid t o CrzOs; or I part 1 Campbell and Andrews, J . A m . Chem. Soc., 11 (189.5). 126; Moore, Chem. News, 12 ( l e g s ) , 92; Goutal, Z . angew. Chcm.. 177 (1898); Brearley F e = 0.3107 part Cr. The ferrous ammonium suland Jarvis, Chem. News. 18 (18981, 177; Johnson, J . A m . Chcm. Soc., 29 fate contains 14. 2 j per cent of ferrous iron; therefore (1907). 1201; Campbell and Arthur, I b i d . , SO (1908). 1116; Grossman, and 5 cc. of hydrofluoric acid, dry, ignite, a n d weigh; again moisten with sulfuric and 5 cc. hydrofluoric acids, dry, ignite, and weigh, repeating, if necessary, t o constant weight. The loss in weight is silica. This weight multiplied by 0.4693, divided by 2. j times I O O gives the per cent of silicon. Dissolve t h e residue, left after t h e volatilization of the silica, i n t h e platinum crucible with about I O cc. of concentrated hydrochloric acid a n d a few drops of nitric acid, and heat. If any of t h e residue remains undissolved, dilute the acids carefully, decant through a filter, dry t h e residue thoroughly, mix with about 15-20 times its bulk of sodium peroxide. and fuse until t h e contents of t h e crucible are liquid, then cool, dissolve in dilute hydrochloric acid (I : 3) and combine the solution with t h e former filtrates. Transfer t h e combined filtrates t o a j o o cc. volumetric flask and make u p t o mark. This is t h e “stock” solution.
Chcm.-Zfg., 82 (1908). 1223.
1
Adapted from Spuller and Brenner. Chem.-Zfg.,21 (1897), 3-4.
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I part of the salt equals 0.04427 part Cr. If X equal the amount of ferrous ammonium sulfate used, I cc. of t h e permanganate equal T g. of ferrous ammonium sulfate used, a n d assume y cc. of permanganate were used in titrating A grams of the sample, then the per cent of chromium is found by the following equation: Per cent Chromium = ( X - T y ) 4.427/A
MANGANESE
Evaporate I O O cc. of the “stock” solution almost t o dryness, take u p with concentrated nitric acid, and evaporate t o about half the bulk. Precipitate the manganese with 5 g. potassium chlorate, and evaporate t o small volume, adding potassium chlorate a second time. Dilute the solution with water, filter through a thin layer of asbestos on a Gooch filter, and wash thoroughly with water. Transfer the precipitate and asbestos t o a beaker, a d d ferrous ammonium sulfate from the burette until the precipitate is dissolved, dissolve with ferrous ammonium sulfate, the precipit a t e clinging t o the sides of the crucible, and wash the crucible thoroughly with hot water. Titrate the excess of ferrous ammonium sulfate with permanganate. Metallic iron times 0.3918 = Mn. The per cent of manganese may be found by the following equation, where X is t h e number of grams of ferrous ammonium sulfate used, y the iron equivalent per cc. of the permanganate solution, T the cc. of permanganate used, 14.25 t h e per cent of iron in ferrous ammonium sulfate, a n d A the grams of the substance used. Per cent Manganese = (0.1425X - T y ) 49.18/A ZINC’
STANDARDIZATION OF THE POTASSIUM F E R R O C Y A N D E
-Weigh about 0.2 g. of pure zinc into a flask and dissolve in hydrochloric acid. When the zinc is dissolved, dilute with about 50 cc. of water, neutralize with ammonium hydroxide a n d after making slightly alkaline acidify with hydrochloric acid, adding a slight excess. Dilute t o about 2 5 0 cc., heat t o 7-80’ C., and titrate with potassium ferrocyanide solution as follows: place about one-third of the zinc solution in a 400-500 cc. beaker and titrate with potassium ferrocyanide until a drop, when removed and tested on a porcelain color plate with the uranium solution, shows a brown tinge; add another third of t h e zinc solution and continue the titration until the end-point is passed; then a d d the last portion and finish the titration very carefully. The reaction is sharper if several drops are taken for the end-point. A correction should be made for the amount of ferrocyanide required t o produce the color when no zinc is present. The equivalent per cc. of t h e ferrocyanide is thus obtained. THE DETERMINATION-Evaporate the filtrate from the iron-chromium precipitation almost t o dryness, take up with concentrated nitric acid, evaporate t o about half bulk, add 2-3 g. of potassium chlorate, boil for a few minutes, dilute and filter through a Gooch filter. Neutralize the filtrate containing zinc and 1 Adapted from Fahlberg’s method, E. Prost, 2. anal. Chem., 460 1896); Chem. News, 76, 6.
Vol. 9, No. 5
nickel with ammonium hydroxide, heat to boiling, and add 2 0 t o 30 cc. of a I per cent solution of dimethylglyoxime. Allow the precipitate to settle and filter through a Gooch. Neutralize the filtrate with hydrochloric acid, a d d a slight excess, and heat the solution t o jo-80’ C. Conduct the titration as described under the standardization of potassium ferrocyanide. CARBON
The carbon may be determined by direct combustion in a current of oxygen, and by the apparatus described by Blair, “ T h e Chemical Analysis of Iron and Steel,” 7th Ed., 1912,p. 134. The writer is indebted t o Dr. C. S. Palmer for his kindly advice and helpful suggestions during t h e progress of this work. MELLON INSTITUTE os INDUSTRIAL RESEARCH UNIVERSITY OF PITTSBURGH
A SIMPLIFIED INVERSION PROCESS FOR THE DETERMINATlON OF SUCROSE BY DOUBLE POLARIZATION’ By HERBERT S. WALKER Received November 4, 1916
Probably the greatest drawback t o the use of “true sucrose” determinations in sugar factory control work has been the necessity for such extreme care in the regulation of time and temperature required b y the Herzfeld-Clerget inversion process. So sensitive t o faulty manipulation is the method ordinarily used t h a t a n inexperienced chemist may get even less accurate results by double polarization than by simply assuming the direct polarization t o represent “true sucrose.’’ T o avoid any decomposition of fructose during inversion, Tolman* suggested inverting a t ordinary laboratory temperatures. This method has never been largely adopted in cane sugar factories, owing to the fact t h a t a t least I O hrs. are required for t h e complete inversion of t h e half-normal weight of pure sucrose in 50 cc., and probably a considerably longer time would be needed where organic impurities are present, as in the case of waste molasses. Steuerwalda has also proposed inverting in the cold, and shortens the time required t o 2 or 3 hrs. by using three times the usual quantity of acid (30 cc. of a mixture of equal parts concentrated HC1 and water). The convenience of using a diluted acid will be appreciated by anyone who has had t o measure many successive portions of concentrated HC1 with the same pipette. Steuerwald’s method, however, as pointed out by Pellet4 when dealing with impure cane or beet products, accentuates the error inherent in the Herzfeld-Clerget process in t h a t optically active substances other t h a n sucrose may, in a strongly acid medium, have quite different rotation from t h a t indicated i n a neutral or slightly acid solution used for direct polarization. I Presented a t the Annual Meeting of t h e Hawaiian Chemists’ Association, October 12, 1916. 2 U. S. Bur. Chem., Bull. 73, 69. 8 Archief, 1913, 831. 4 I. S. J.. 1916, 83.
