Dec., 1919
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
illustrate these points are herewith given. Indefinite a m o u n t s of iron were used with each sample of copper. T h e solution of K M n 0 4 ( 7 g. per 1.) on determination gave P e value of I cc. = 0 . 0 1 2 0 7 .
8 9 10 11 12
0.0138 0.0276 0.0326 0.0527 0.0670 0.0834 0.0917 0.1214 0.1432 0.1625 0.1912 0.2000
7.9 13.9 16.4 26.5 33.9 42.1 46.1 61.0 71.9 81.4 96.2 100.3 Average =
Hence, t h e actual copper = 0 . 0 1 2 0 7 X 0.1646 = factor is 0.1646 a n d t h e ference is probably d u e cuprous thiocyanate.
0.001972 0.001985 0.001987 0.001988 0 . 0 0 197 7 0.001982 0.001988 0.001990 0.001992 0.001996 0.001988 0.001992 0.001986
Cu : ‘Fe 0.1634 0.1645 0.1647 0.1647 0.1638 0.1642 0.1647 0.1649 0.1651 0.1654 0.1647 0.1650 0.1646
Gram 0.0139 0.0256 0,0326 0.0526 0.0674 0.0836 0.0916 0.1212 0.1428 0.1617 0.1911 0.1994 ~~~~
value of t h e pgrmanganate 0.001986, t h u s t h e actual theoretical 0.1626; the dift o t h e slight solubility of
S O M E O B S E R V A T I O N S O N THE P R O C E D U R E
*
I-The strength of permanganate solution, 7 g. per l., as used above, was selected because I O cc. closely equals I per cent copper on a 2-g. sample of ore. This is a very strong solution, about three times t h a t usually used for t h e titration of iron, yet I cc. equals only 0.1 per cent copper; hence i t is very easy t o check t o 0 . 0 2 per cent copper (on low-grade ores). Slight irregularities due t o filter papers, etc., do n o t appreciably affect t h e results. However, the 5 cc. concentrated hydrochloric acid should n o t be added t o t h e liquid being titrated until t h e end is nearly reached in order t h a t enough manganese sulfate may be present t o act as acceptor between the ferrous iron and t h e permanganate. a--The precipitation of t h e cuprous thiocyanate from about a z per cent sulfuric acid solution (other acids having been removed b y evaporation t o sulfur trioxide fumes) has been found satisfactory. A solution containing 4 per cent sodium thiocyanate a n d I O per cent sodium sulfite is used as precipitating agent (IO cc. of this usually suffices for most samples). 3-Unless t h e insoluble residue is very white i t is advisable t o remove i t b y filtration before precipitating the cuprous thiocyanate. 4-The solution containing t h e cuprous thiocyanate should be boiled t o coagulate t h e precipitate. It m a y then be readily filtered on a coarse paper t h a t has received t w o or three small washes of a “filler.” This filler is made by agitating I g. of corn starch (cooking starch) with I 1. of water. This is a mechanical filler a n d does not relieve one of t h e necessity of using a few drops of sulfuric acid in t h e h o t water used t o wash t h e precipitate t o prevent formation of a hydrosole. 5-This starch filler h a s been found t o insure very clear filtrates even when using coarse filter paper. T h e a m o u n t used has n o t been observed t o consume a n y appreciable q u a n t i t y of permanganate either b y itself or by possible products of its hydrolysis under t h e conditions of t h e procedure. 6 - T h e titration seems t o be effected most accurately
1139
in t h e solution volumes previously indicated. If larger amounts of copper are being titrated i t would be better t o use stronger permanganate. SUMMARY
A modification of t h e usual permanganate method for copper is presented whereby ( a ) the theoretical ratio of copper t o iron is reduced from 0.1897 t o 0.1626; ( b ) t h e actual ratio factor is found t o more closely approach t h e character of a linear coefficient; (c) t h e procedure seems in many cases t o be more rapid a n d t o give more accurate results. POTRERILLOS LABORATORIES POTRERILLOS, CHILE
THE USE OF NICKEL CRUCIBLES FOR THE J. LAWRENCE SMITH FUSION IN DETERMINING SOIL POTASSIUM B y SETHS. WALKER Received July 7, 1919
T h e scarcity a n d high price of platinum during t h e war led t h e writer t o investigate t h e feasibility of substituting nickel crucibles for platinum ones in fusing soils b y t h e J. Lawrence Smith method for total potassium. There would seem t o be no theoretical reasons against t h e use of nickel for this purpose. Still, it is noticeable t h a t wherever t h e Smith fusion method is described in t h e literature platinum crucibles are specified, a n d in view of this t h e writer did n o t feel justified in making t h e substitution without experimental proof of its adequacy. Accordingly duplicate fusions were made on a number of soils, using a platinum crucible for one duplicate a n d a nickel crucible for t h e other. I n all cases 0.5 g. of d r y soil was t a k e n a n d thoroughly mixed with 0.5 g. of ammonium chloride a n d 4 g. of calcium carbonate by grinding in a n agate mortar. T h e mixtures were fused (after t h e usual preliminary heating t o expel ammonia) for 45 min. a t t h e highest h e a t obtainable with a good Bunsen burner. T h e subsequent operations were essentially as described b y Ames a n d Gaitherl a n d were carried o u t alike for all determinations. Porcelain dishes were used for the final evaporation with platinum solution. T h e potassium precipitates were collected on Gooch crucibles a n d dried in a water oven. T h e following table shows the weights of potassium chlorplatinate found by t h e t w o methods. WEIGHTS OF K2PtC16 FOUND BY FUSING SOILS IN PLATINUM AND IN NICKEL CRUCIBLES KIND O F CRUCIBLE Platinum Nickel SOILN o . Gram Gram 0.0142 0.0145 S-223 0.0082 5-254 0.0178 5-255 0.0175 0.0098 0.0096 S-258 0.0118 S-259 0.0118 0.0032 S-260 0.0034 0.0038 5-262 0.0037
{E;;
DISCUSSION
O F RESULTS
I n only one case, v i z . , Soil S-255, was there a n appreciable difference in the weights found; a n d when t h e comparison was repeated on t h a t soil, results were obtained which not only agreed between themselves, b u t also with t h e result previously obtained with t h e 1
Ohio Agr. Expt. Station, Ballstila 861, 507.
I 140
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
nickel crucible. This indicates t h a t t h e discrepancy at first observed was due t o some undetected error i n manipulation with t h e platinum crucible fusion, r a t h e r t h a n t o inadequacy of t h e nickel crucible. Although, as shown, correct results are obtained b y using a nickel crucible, i t cannot be claimed t h a t nickel is as satisfactory as platinum. T h e nickel crucibles are decidedly attacked b y t h e fusion mixt u r e , so t h a t t h e life of a crucible is rather short. The inner surface of t h e crucible soon becomes rough and Pitted, making it somewhat difficult t o remove the mass cleanly. T h e fused mass is always colored green by dissolved nickel, a n d i t does n o t slake a n d disintegrate as well as those from platinum crucibles. But,
Vol.
1 1 , No. 1 2
as also mentioned b y Ames and Gaither,l poor slaking does not affect t h e final result. SUMMARY
I t is found t h a t t h e s a m e result for soil potassium is obtained whether t h e soil is fused i n a platinum or a nickel crucible. Nickel crucibles are attacked b y the J. Lawrence S m i t h fusion mixture a n d a r e therefore not as satisfactory as platinum crucibles. SOILLABORATORY p+h
LOUISIANA AGRICULTURAL EXPERIMENT STATION “, :BATON R ~ ~ LOUISIANA ~ E ,
____ 1 LOC.
cit.
ADDRESSES AND CONTRIBUTED ARTICLES CHEMICALS RECEIVED BY THE BUREAU OF CHEMISTRY DURING THE WAR*
by means of morphine were futile. All samples of carbon tetrachloride examined contained carbon disulfides. Other liquid organic reagents have been of less excellent quality. B y H. E. Buc Good methyl alcohol is obtainable, but not without a t least For a good many years the Bureau of Chemistry has been traces of acetone. Amyl alcohol of good quality is not to be regularly examining all the stock chemicals purchased. Without had. Not only does it contain appreciable amounts of pyridine going into a detailed account of this work, initiated by Dr. I,. but the boiling range is very wide. This is also true of amyl F. Kebler and carried on under his charge, it may be said that acetate. Pure benzene seems to be non-existent. Thiophene during the period of half a dozen years preceding the war the and carbon disulfide are always present, and quite often the chemical reagents on the market, mostly of American make, boiling range points to the presence of homologs. were quite generally of excellent quality. During the first year “Absolute” organic chemicals (free from water, etc.) are of the war, according to our records, there was no marked change. generally unobtainable. This is true of acetic acid, methyl Since that time, however, the Bureau has had considerable difficulty in procuring good chemicals belonging to certain alcohol and ethyl acetate, which are occasionally desired in classes, and we have been occasionally disappointed with chem- absolute or nearly absolute condition. We prepare our own absolute ethyl alcohol (not less than 99.8 per cent), having icals belonging to types that generally come quite pure. The writer’s experience covers a period of four years, 1915- started to make it ourselves long before the war, owing to the fact that we were unable to procure a dependable grade. 1919. During that time about 1300 samples were examined. In the case of absolute ether, for the most part the products Of these about 150 shipments were found to be more or less sent to us are good. Occasionally we are obliged to reject unsatisfactory. During a similar preceding period of four years, samples which show turbidity when treated with sodium. Our 1911-1915, during which a like number of chemicals were tested, only about 50 were unsatisfactory. Too much importance experience with the preparation of this product, which a t one time we did ourselves, indicates the necessity of thoroughly should not be attached to the proportion of 150 to 50 as the kinds of chemicals tested were not exactly parallel. On the washing out the alcohol in the preliminary stage. A heavy test for aldehyde seems always to accompany the turbidity obtained other hand, in the latter period, in addition to the above 150, with sodium. a number of tests were made of samples submitted by dealers. Acetic acid (99.9 per cent) complying with the dichromate When these were found unsatisfactory, the agents or manufacturers were so informed, thus diminishing the number of ship- test requirement is now unobtainable; but even before the war ments of unsatisfactory chemicals. It should also be added this grade was not easy to get. The best grade which we can obtain a t present, and that from only one firm, is labeled 99.5 that the shortcomings of the chemicals tested in the war period per cent, but is actually a little higher. Samples that have were more serious than those recorded in the pre-war period. reached’us from other firms rarely go above 99.0per cent. A more detailed comparison between the two periods is hardly ALKALI SALTS-This embraces a number of common and necessary. The main purpose of this paper is to point out the present situation in regard to ordinary reagents, as shown by important reagents. For the most part they are of good quality, the examinations made in the Bureau of Chemistry. For the but certainly not dependably so. We have on record sodium purpose of this discussion the chemicals may be divided into chloride with quite a little magnesium present, and ammonium chloride leaving a high residue on ignition. several classes which differ widely in quality. “Anhydrous” alkali carbonates seldom have less than 8 to LIQUID INORGANIC CHEMICALS-Hydrochloric, Sulfuric, nitric, I Z per cent of water. Sodium and potassium hydroxides, parand phosphoric acids, and ammonia, generally have met our ticularly the latter, a t one time gave us considerable trouble. requirements. LIQUID ORGANIC CHEMICALS-The ordinary alcohol, ether, The quality coming in now is fair, except for too strong a test acetone chloroform, carbon tetrachloride, carbon disulfide, for chlorides. Incidentally, it should be said that the strength and glycerin have been found satisfactory for practically all of these chemicals is higher than is commonly supposed. Sodium chemical purposes. On evaporating large quantities of ether hydroxide comes about 97 per cent potassium hydroxide, hardly the penetrating odor of formaldehyde is often perceived in the ever falls below 86 per cent and occasionally goes above go per last portions. However, attempts to identify formaldehyde cent. Potassium permanganate, long a source of worry to our purchasing office, now comes in good quality, in spite of a rather 1 Presented before the Division of Industrial and Engineering Chemistry novel appearance and color. Occasionally, however, it bears a t the Philadelphia Meeting of the American Chemical Society, September more than traces of chloride. 2 t o 6. 1919.
