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which is approached with some hesitation, b u t t h e lowing conclusions regarding t h e cupellation for base whole object of t h e investigations upon which this metal: There are two chief sources of operative error paper is founded is for the purpose of improving our in this determination, t h e absorption of gold and silver assaying methods as necessarily carried out under by t h e cupel a n d t h e retention of base metal b y t h e commercial conditions, a n d before this can be intelli- precious metal button. At present we do not have gently undertaken or successfully accomplished i t is t h e means of controlling either of these with a n y ceressential t o consider all t h e conditions surrounding tainty, or of readily ascertaining their extent in comour present methods and their application. It be- mercial work. These errors may balance each other, comes, therefore, essential t o consider t h e human as- b u t they often fail t o do so. A low cupel absorption pect of the work, since a large laboratory is liable t o may be accompanied by either a high or a low b u t t o n contain a variety of personalities. Without going into retention, or a high cupel absorption by either kind details, three chief factors may be mentioned under of button retention, a n d t h e relations may be reversed this head: pure carelessness, laziness and t h e domina- in t h e duplicates. A third defect arises from t h e fact tion of one’s own or a n outside will or intellect. The t h a t the proofs are subject t o t h e same uncontrollable first one may cause agreement or disagreement, b u t errors as t h e assays, a n d t h e proof corrections may be the second two may surely be counted on to unify the fallacious. resu 1t s , Notwithstanding t h e defects pointed out in this One of t h e best assayers I have ever known, who was paper, which render t h e method unsatisfactory, t h e also big a n d strong enough t o be frank, once said t o me: simplicity and ease of execution of t h e cupellation “ W h y I can see a n y weight a t t h e balance t h a t I method commend its use a n d undoubtedly i t will want to.” The records of t h e Bureau, particularly be extensively employed for many years t o come. I t the older ones, show far too many cases of remarkable is also evident that t h e defects are inherent a n d t h a t agreement in t h e reported results t o be explained simply there is no apparent way of ov8rcoming t h e m in t h e upon t h e general theory of chance. present state of our knowledge. I t , therefore, becomes I n one case a sample was sent t o a n institution on necessary t o seek for a better method, and preferably two occasions a n d assayed i n quadruple each time. a direct determination of t h e silver. Everyone of the eight results reported was 0.2 j fine in silMoreover, aside from the ordinary errors of manipuver. The same sample was sent again a n d t h e duplicate lation, t h e presence in a bullion of members of the plat results were both given as 4 fine in silver. It was sent inum group of metals, which are soluble in nitric again and all four results were stated as j fine in silver. acid when alloyed with silver, further complicates I n t h e case of the arsenical bullion already mentioned t h e determination of t h e silver by cupellation. Such one laboratory reported t h e silver a t Ioj, 1 0 5 , 106 and bullions are not uncommon in Mint work, Athough 1 0 7 , b u t on another occasion i t was reported by t h e much of the platinum occurs in scrap material pursame laboratory at 106, 109, I I O a n d 1i4. I n all, chased. 24 determinations of silver were made on this sample ( T o be c o n c l u d e d ) in five laboratories a n d they varied from I O I t o 1 1 7 . Another laboratory shows surprising agreement beTHE DETERMINATION OF CHROMIUM AND MANtween duplicates all along t h e line. A difference of GANESE IN IRON AND STEEL 0 . j in t h e base-metal duplicates is rare, b u t when their By FREDC . T. DANELS samples are sent t o other institutions for assay, much Received May 6 , 1914 wider differences are reported, and on one occasion I n steel furnace operations i t is frequently necessary in this laboratory a proof composed of j80 gold, to include chromium among elements t o be determined 400 silver and 20 copper lost 20, while a companion in t h e preliminary analysis. The following zo-minute proof of t h e same composition lost only 8. Also a method has been worked out t o fill this necessity. sample of proof gold was once sent t o this institution, I t has been in constant use for t h e past two years a n d under the name of fine gold simply, a n d t h e report is sufficiently accurate t o be used as a daily routine showed 999. j , 999.6, 999.7 and 999.7 fine in gold. Finally method, a n d i t occupies b u t little of t k e chemist’s in various comparisons t h e results from this institution actual working time. form a closely agreeing group of figures a t one or t h e The method for chromium is a n adaptation of t h e other extreme of all t h e reports in t h e comparison. persulfate method for t h e manganese determination I n one instance a docile weigher sitting by t h e side in iron a n d steel. of a domineering personality turned in many consecuThe method for manganese is the persulfate method tive reports agreeing absolutely with the figures of his except t h a t t h e sum of t h e manganese and chromium associate. is obtained in this titration a n d the manganese calcuCONCLUSIONS REGARDING T H E CUPELLATION METHOD lated by difference, using the results from t h e chromium Determinations b y difference are always objection- determination. The objection t o the usual persulfate able since all t h e errors of t h e other determinations method for manganese, in t h e presence of chromium, are thrown upon t h e final one. This allows a wide is t h a t a varying quantity of t h e chromium is reduced margin for differences between duplicates a n d leaves along with t h e manganese by t h e ferrous ammonium t h e question of t h e actual amount of t h e estimated sulfate or sodium arsenite. If determined colorimaterial present in doubt. metrically, t h e chromium gives t h e solution a different The mass of data here presented warrants the fol- shade, which is difficult t o compare. This may be
A W . , 1914
T H E J O C R N A L OF I N D L - S T R I A L A N D ENGINEERING C H E M I S T R Y
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overcome by using for a s t a n d a r d a steel containing Inks,’‘ a n d t h e other a circular of general information approximately t h e same a m o u n t of chromium as t h e on this subject. T h e length of these papers is such sample. -4 still more convenient way is t o a d d t h e as t o make i t unwise t o a t t e m p t t o present either of chromium as potassium bichromate, using a s t a n d a r d t h e m in full a t this time, b u t it is desired t o give some solution. so t h a t I cc. would equal 0 . o O o j gram of idea of their scope. chromium, i. e . , o . z j per cent chromium for a 0 . 2 0 T h e first paper t r e a t s t h e subject from a n analytical gram charge of t h e sample. This solution is added t o point of view. Four types of ink have been investit h e s t a n d a r d after t h e solutions have been transferred gated: web press, flat-bed, job, and half-tone inks. t o t h e color comparison tubes. These included a number of colored as well as t h e more CHRo~fIus~LI-WeighI gram of t h e sample into a common black inks. T h e method of analysis has 300 cc. Erlen~lleyer flask ( J e n a glass). a d d I O O cc. been in use f o r several years for t h e testing of supplies nitric acid (1.135 specific g r a v i t y ) , place on t h e hot delivered t o t h e Government Printing Office, a n d has plate, a n d when solution is complete. boil off all nitrous been found very satisfactory for this purpose. fumes. ( T h e volume of t h e solution should not be less Using as t h e solvent a mixture of benzene a n d ethyl t h a n jj cc. It is unnecessary t o filter off t h e silicon ether, the oil is separated from t h e pigment by means a n d graphite residue if t h e solution is complete. When of a centrifuge. I n some cases petroleum ether m a y t h e sample is high in combined carbon, i t is well t o be used a s t h e solvent. This method gives a n effective a d d a few crystals of ammonium persulfate when t h e separation, a n d t h e pigment may be determined with solution is complete a n d boil a moment longer t o des- a fair degree of accuracy. t r o y t h e combined carbon.) Remove t h e flask from T h e oil fraction, after evaporating off t h e solvent, t h e hot plate, a d d 7 5 cc. silver nitrate solution ( 2 . 0 0 is analyzed for unsaponifiable oils (rosin a n d mineral g r a m s per liter), a n d immediately j grams of a m - oils), rosin, hard gums a n d linseed oil. monium persulfate crystals. Replace flask on t h e I n t h e black inks, t h e pigment is ignited a n d t h e ash hot plate a n d bring gently t o boiling. Boil vigorously tested for driers a n d ferric oxide, t h e latter being the f o r a minute, a n d while still boiling a d d dilute hydro- residue left on t h e ignition of Prussian blue. A qualichloric acid, drop b y drop, until t h e permanganate tative test for Prussian blue is given, which will decolor is completely destroyed. Continue t h e boiling tect less t h a n one per cent of this material in t h e pigfor one minute a n d t h e n cool t h e flask immediately ment. If aniline dyes are present, t h e y may be dein water. T i t r a t e by adding a n excess of t e n t h - termined by extraction b y means of alcohol, unless normal ferrous ammonium sulfate solution above t h a t preliminary examination shows t h a t t h e dye is insoluble required t o reduce t h e chromium, a n d t i t r a t e back in this solvent. I n t h e l a t t e r event, a suitable solvent with tenth-normal potassium permanganate solution. must be found. T h e number of cubic centimeters of t h e ferrous a m T h e colored inks require a preliminary examination monium sulfate oxidized by t h e chromate, multi- t o determine t h e nature of t h e pigment used, a n d t h e plied b y 0.00174,gives t h e weight of chromium in t h e method of a t t a c k depends largely upon t h e results of sample. these tests. Some of t h e mineral pigments, such as M A K G A N E S E I N T H E P R E S E N C E O F CHROMIVM-Provermilion (mercuric sulfide) a n d chrome green (i. e . , ceed according t o t h e above directions for t h e deter- t h e material known commercially as Brunswick or mination of chromium except t h a t after t h e ammonium Milori . Green), ‘may be determined quantitatively persulfate is added, only h e a t until t h e solution just according t o t h e procedure outlined in t h e original comes t o boiling, t h e n cool immediately a n d t i t r a t e article. If t h e coloring matter consists of aniline a s before, this time adding enough ferrous ammonium dyes or lakes, i t will usually be found sufficient t o sulfate t o reduce both t h e manganese a n d chromium. determine whether or not these colors are fast t o light. T h e number of cubic centimeters of ferrous ammonium Two methods for this test are given. sulfate used, minus t h e number used in t h e chromium A table is given showing how closely one may expect determination, multiplied b y 0.00j j, equals t h e weight duplicate determinations on t h e same sample t o check. of manganese in t h e sample. These figures are t h e result of testing several hundred The ultimate value of t h e solutions may be used in samples of ink b y a t least half a dozen analysts, so calculations as above. I n this case it is advisable t h a t they may reasonably be t a k e n as a fair mer-sure t o carry along a blank with a sample containing no of t h e accuracy of t h e method. chromium a n d subtracting t h e blank. T h e s t a n d a r d The paper also includes a brief discussion of t h e ization of t h e solutions against a s t a n d a r d steel is t h e relation of these laboratory tests t o t h e practical t e s t s most satisfactory procedure. which may be made b y t h e printer. It is not t h e in\ V ~ E E L I N GMOLD& FOITDRY Co tention t h a t t h e latter shall be supplanted by t h e forI\ HEELING. \%’EST \-IRGIhIA mer, b u t t h a t t h e two shall supplement each other in order t o obtain t h e grade of ink which is t h e most PRINTING INKS AND THEIR ANALYSIS’ suitable for t h e purpose. B y J. B TUTTLE A N D W.H. SXITH Received April 16, 1914 T h e second paper is t h e circular of information on There will be published shortly b y t h e Bureau of t h e general subject of printing inks. I t gives a brief Standards, t w o papers on t h e subject of printing inks: description of some of t h e materials used in t h e manuone, a technologic paper on “ T h e Analysis of Printing facture of ink, a n d also t r e a t s broadly some of t h e problems concerning t h e relation between t h e ink 1 Published by permission of the Director of the Bureau of Standards.
