T H E J O U R N A L OF I.VDLTTRIAL A N D ENGINEERIIYG C H E M I S T R Y . lated cold-water extracts. Sample H, on the second day, gave somewhat higher results for inorganic phosphorus than on the first day immediately after the death of the animal. This was probably due to enzyme or bacterial action, or to both. The cold-water extract from sample b, Table I , contained 0.119 per cent. inorganic phosphorus after coagulation. This extract after boiling for z hours with 0 . 2 per cent. HCI gave 0 . 1 2 1 per cent. of inorganic phosphorus, but determinations made after the extract had stood 36 hours in the laboratory gave a result of 0.141 per cent. inorganic phosphorus. Either enzymes or bacteria, or both, increased the inorganic phosphorus one-sixth of the original amount, while boiling with acid made no appreciable difference. This is in accord with results obtained b y Siegfried and Singewald. CONCLUSIONS.
Stanley and Trowbridge's determinations of organic phosphorus b y the barium method are too high on uncoagulated extracts on account of barium phosphate passing through the filter. The temperature of boiling water has very little hydrolyzing action on the organic compounds of phosphorus in animal tissues. Enzymes and bacteria seem to exert more of a hydrolyzing influence on organic phosphorus compounds of animal tissues than does boiling. Coagulation of the proteids b y boiling the extracts of tissues serves two purposes: ( I ) i t clears the solution-a more complete precipitation resulting; ( 2 ) i t arrests the action of enzymes and bacteria. ACKNOWLEDGMENTS.
The author wishes to express his gratitude to Dr. E. B. Forbes for making this work possible and for assistance and suggestions rendered during this study. '
DEPARTMENT OF NUTRITION, OHIOAGR EXPT STATION, WOOSTER. OHIO
A VOLUMETRIC METHOD FOR ANTIMONY I N ALLOYS. By GEORGES. JAMIESON.
The object of this paper is t o describe a n application of L. W. Andrews' iodate method1 t o the determination of antimony in alloys, particularly "hard leads" and solders. The method is satisfactory because i t is not interfered with by copper and iron, metals which frequently occur in small quantities in these alloys, and because i t is rapid and accurate. Two other iodimetric methods have been compared with this b y the writer with less satisfactory results. The first, which is based upon getting the antimony into the pentavalent form in dilute hydrochloric acid solution, adding potassium iodide and titrating with sodium thiosulphate, gave good results in the absence of copper and iron, but was unsatisfactory in the presence of these metals. The other method, depending upon getting the antimony into the trivalent state in a sodium bicarbonate solution and J . A m . Chem. SOC.,26, 756
(1903).
April,
1 9 1I
titrating with iodine was found t o give poor results, particularly with alloys containing much lead, as even when tartaric acid is used, the lead carbonate precipitate appears to hold antimony, thus causing low results. Andrews showed' t h a t his iodate method was satisfactory for antimony b y applying i t to pure tartar emetic. The method has been further tested b y the writer by dissolving weighed quantities of Kahlbaum's pure antimony in concentrated sulphuric acid and titrating it as described beyond. It is t o be observed t h a t this titration is carried out in the presence of 1 5 - 2 0 per cent. of actual hydrochloric acid, which gives iodine monochloride as the endproduct, according t o the equation 2SbClg KIO, 6HC1 = zSbC1, KCl IC1 gH,O. The potassium iodate solution which was used throughout the entire investigation contained 3.5667 grams of KIO, per liter, corresponding t o 0.00400 gram of antimony for I cc. The following results were obtained:
+
Sb taken. ; Gram. 0.1000 0,1000 0 ,0490
+
KIOiused. 24.85 24.90
12.20
+
+
+
Sb found. 0 ,0994 0.0996 0.0488
The following method of analysis for alloys has been worked out: Take 0.5 gram of alloy in the form of drillings or chips' in a zoo cc. Erlenmeyer flask. Add I O cc. of concentrated sulphuric acid and heat until the alloy is entirely decomposed.3 Boil the solution gently for about 2 minutes after the lead sulphate has become white, allow the solution to cool to room temperature, dilute with 1 5 cc. of cold water, allow to cool somewhat, add 15 cc. of I : I hydrochloric acid, shake thoroughly and filter off the lead sulphate on a Gooch crucible, washing with small quantities of the same hydrochloric acid. Transfer the filtrate t o a glass stoppered bottle of about 2 5 0 cc. capacity, add 5 cc. chloroform, 15 cc. of concentrated hydrochloric acid,4 and 5 cc. of iodine monochloride s ~ l u t i o n . ~ Shake the titration bottle, let it stand for about five minutes and then titrate the liberated iodine with standard potassium iodate solutiona until the chloroform is just decolorized after thorough shaking, which should be repeated in about a minute to make sure of getting the true end point. To make a second titration most of the liquid may be poured off, leaving the chloroform ready for use. It should be observed that, as Andrewsl has shown, cit. I f the alloy contains less than 2 per cent. of antimony, it is better to take 1 gram or more, while with alloys very rich in antimony 0.1 or 0.2 gram will suffice. a If the flask is covered with an inverted porcelain crucible cover. the dissolving and boiling may be carried out without the escape of any disagreeable quantities of fumes, 50 that the hood need not be used. 4 To allow for dilution with the standard solution. li To prepare this solution, dissolve 10 grams of potassium iodide and 6.44 grams of potassium iodate in 75 cc. of water, add 75 cc. of concentrated hydrochloric acid, then add a globule of chloroform in a glass stoppered bottle, and adjust exactly to a faint iodine color by shaking and adding dilute potassium iodide or potassium iodate solution as the case may require. 6 I f the volume of potassium iodate solution used is much over 15 cc., i t is advisable to add more concentrated hydrochloric acid to keep the strength near the 1 : 1 point. 1LOC.
2
DUBOIS A N D LOTT ON COCOA S H E L L S I N COCOA POWDER. the strength of the hydrochloric acid solution in which the titration is made is of much importance. The directions, therefore, as given above should be closely followed in regard t o the strength and amounts of hydrochloric acid used. The following results were obtained with a number of alloys: No.
Weight taken.
1A
0.2000 0,2000 0.2000 0.2005 1 .oooo 1 .oooo 0.5000 0,5000 1 .0000 0.5000 0.5000 1 .oooo
2-4
1B 2B
1c 2c 1D 2D
1E 1F 2F 1G
CC.
Per cent. Per cent. of Sb by of Sb. thiosulphate meth
KIOa used. 6.70 6.70 6 .OO 6.03 2.70 2.70 5.90 5.90 2.40 2.85 2.85 2.80
13.40 13.40 12.00 12.03 1 .08 1 .08 4.72 4.72 0.96 2.28 2.28 1.12
13.43
...
12.07
... ...
1.04 5.11'
... 0.96 2.32
...
1.16
The first two alloys are antimonial leads and the others are commercial solders, some of which were of poor quality on account of the antimony present. The time required for a n analysis was about a n hour. Arsenic is rarely present in appreciable quantities in the alloys under consideration, but it is to be noticed that, if present, it would be titrated with the antimony. The following results were obtained b y dissolving metallic arsenic in concentrated sulphuric acid and proceeding exactly according to the method that has been given. As taken. Gram.
KI08 used. cc.
As found.
0.0100 0.0100 0,1019
4.10 4.10 40.60
0.0102 0.0102 0.1015
I n a case where an alloy contains an appreciable amount of arsenic it is best t o carry out the process exactly as directed as far as filtering off the lead sulphate and washing it with I : I hydrochloric acid. Then pass in hydrogen sulphide t o precipitate the arsenic, pass air through the liquid for half an hour or so t o remove the hydrogen sulphide and t o oxidize any iron that may be present, filter, wash with I : I hydrochloric acid, and titrate as usual. This process was tested b y the use of alloys mixed with known quantities of pure metallic arsenic with the following results: Alloy taken. Gram. 0.5000 0,9560 0.2000 0.2000 1 .oooo
As taken. Gram.
Per cent. Sb found.
0.0050 0,0118 0.0460 0.0520 0.0097
4.72 4.77 12 .oo 12.10 1.04
Per cent. Sb in alloy. 4.72 4.72 12.00 12 .oo 1 .08
SHEFPIELD LABORATORY, NEW HAVEN. CONN.
-----
25'
depends upon the fact that the heavier constituents of cocoa shells sink in a solution of calcium chloride of specific gravity 1.535,whereas the lighter constituents of the cocoa float in the same. The parts sinking are dried and weighed. Goske determined the amount of heavy material in a number of varieties of cocoa shells of known purity and found this value to vary from 15.4t o 38.76 per cent. on the fatfree shell. The highest figure is taken as the basis of calculation when applying the method to cocoa. The weight of the heavy shell constituents, calculated t o fat-free cocoa, is divided by the factor 38.7 and multiplied by 100, t o give the percentage of shells in the cocoa. I n studying this method, the writers determined factors on a number of varieties of cocoa shells, after extracting the fat. I n the table below is given the results obtained: No. 1 2 4 5 6
7 8 9 10 11 12 13
Percentage heavy constituents, sp. gr. over 1.535.
Variety of cocoa shells. Maracaibo Guayaquil Caracas Bahia African Sancher Surinan Java Amba Venezuela Trinidad Pto Cabello
22.72 21.26 32.32 39.68 31.44 36,66 43.52 42.7 39.46 33.62 52.2 48.12
The average of the figures above is 36.96. The factor selected, therefore, for the determination on cocoa powders was 37. I t will be noted that shell No. 2 showed the lowest percentage of heavy constituents, No. 1 2 the highest, and that No. 7 was the nearest to the average. These three shells were added in known quantities t o a cocoa powder on which the fat and shell contentthe latter by Goske's method-were first determined. With these mixtures Goske's method was followed identically as laid down, with the results shown in the table below, using factor 37 : Sample. 2x 2u
zc 7-4 7B
7c 12A 12B 12c
Percentage shells added. 4.55 10.
12. 4. 9. 14. 2. 6. 10.
Total shells found.
Percentage added shells found.
10.56 15.6 15.7 13.0 12.5
19.1 9.9 16.3 21.5
33.12 8.2 8.3 5.6 5.1 11.7 2.5 8.9 14.1
Total shells found on the cocoa used for this experiment was 7.44 per cent. This value was deducted from total shdls found in the above mixtures to give the value for added shells expressed in the last column.
DETERMINATION OF COCOA SHELLS IN COCOA POWDER.
DISCUSSION O F RESULTS.
B Y W. L. DUBOISAND C. I . L o n .
I t will be seen a t a glance that the results are neither uniform nor accurate. This could well be expected, however, when the great variation in heavy constituents in the various grades of shells is considered. Goske examined seven samples and obtained the range of results cited above. The writers secured values which were uniformly higher than those shown
Received January 28, 1911.
The work herein described was undertaken t o test a method proposed by Goske.9 This procedure Solder D contained a little copper or iron which caused the thiosulphate method to give high results. Also alloys A and B were found t o contain traces of copper. 2. .Vahr. Genussm, 19, 154;C. A , . 4, 1328 (1910).
