GENERAL, PHYSICAL .?NU INORGANIC.
2\50
safely used in the estimation of phosphates in the presence of the above salts. Salt.
Parts per millioti. Concentration, normal.
Socliutii sulphate, deca1iytlr:tte I'otassiuni nitrate . . . . .. llagnesiurn sulphate (hydrate). . . . Potassiuiii hydrogen sull)hate. . . . . Calcium nitrate .. Magnesinm nit ; i l e ... Sodium chloride. . . . . . .. . . . Potacsiuni ethyl sulpl~ate ... Sodium nitrate . .. .
j"" 1000
C)
.003
I).OI
I ooo
ri
I500
0.02
008
2000
0.o j
7000
0
3000
0.035 0 035 0 oh
3000 \j000
.0 3
The results here presented supplement the u-ork of Yeitch' who showed that ammonium salts, and certain chlorides influenced the color of phosphomolyhdate solutions. The data make evident the limitations of this colorimetric method. The oxidation of organic matter with magnesium nitrate, the method recommended by IYiley,? introduces relatively small errors in the estimation of phosphates b y this colorimetric method, for it will be noted, that a coiisiderable quantity of this reagent may be present within certain limits without influencing appreciably the intensity of color. Some experiments have been conducted 1vit.h meat samples in which the material was completely oxidized by electrolytic oxygen and oxides of nitrogen obtained in the electrolysis of concentrated nitric acid. These preliminary experiments indicate that the colorimetric method can then probablp be applied with success, provided the final concentration of acid is made the same as in the solution of standard phosphate used in the comparisons. U'ork on the details of this operation are in progress. This work \vas undertaken a t the suggestion of Dr. Herman Schlundt. I here wish to express my sincere thanks for his kind interest a r ~ lthe assistance he has given me in m y work. Ciiamc.\L
I . . \ B o R ~ T o I ~ ~ -VNIVI:KSI . rs or \ I I s s o r w CI.LXBl.~. 31(> ._ . .~ - ..
NOTES. Out thc Proccdiwr: /os thc Oxidution o j (,'iivonzic A c i d t o I'erchroniic z4cid. ---In the identification of chromium by the oxidation of chromic acid to perchromic acid many, if not all, authors state that the solution should first be acidified with some acid, preferably dilute sulphuric acid, then shaken with an excess of ether, and finally n little hydrogen peroxide added and the whole shaken again so that the perchromic acid formed may be dissolyed in the ether to give a blue color. This method of procedure sometimes proves troublesome. except under certain con-
' Veitcli, L o r ' IYiley.
cif.
" A ~ r i c i l l t ~ i rd~ht l: i l y s i ~ (19001, '' \.
