58 REPORT OF SCHIMMEL & Co. OCTOBER 1915. 
employed in his experiments freshly precipitated mercuric oxide, still sispendarie in 
water, as he had difficulties with the dry substance. The results obtained by wen 
mann after this method were little satisfactory, as he found partly too much, partly 
too little mercuric sulphide, Haselhoff') arrived at the same result at the time. 
Wehrmann did not verify E. Dieterich’s?) method, as, according to the indications 
in the literature, reliable results cannot be obtained by it, but he checked the modi- 
fication by K. Dieterich’). It is clear from his results that it has no essential influence 
on the final outcome, whether the mixture is heated or left cold. One seems to obtain 
somewhat better results by heating, which way is preferable too for the sake of speed. 
It is striking that, following this method, too high results are sometimes obtained, 
a fact which Kuntze*) explains by the content of allylthiourethane in spirit of mustard, 
found especially in old preparations. | 
According to Gadamer®), it is unsuitable to add ammonia first and then einer 
nitrate, as it is the case in Dieterich’s method, for some mustard oil can evaporate 
before the thiosinamine has formed. If on the contrary a mixture of strong ammonia 
with the necessary amount of silver nitrate is added at once, or if such a mixture is 
used in the receiver, the transformation into silver sulphide takes place more quickly 
and with greater certainty. When the reaction is completed, the mixture ought to be 
left standing for 12 hours, so that the silver sulphide can deposit. The results 
obtained by this method were very good, the exactness corresponding about to that of 
Dieterich’s process, which, however, especially if heat is employed, has the advantage 
of greater speed. 
The titrimetric test of the German Pharmacopoeia, 5th edition’), excels by its great 
exactness and reliability, says Wehrmann, and is easily carried out, as s the N/10 silver 
nitrate solution is stable enough for the purpose of titration. 
Roeser’) indicates a method which in its first part corresponds with that of the. 
German Pharmacopoeia. The titration of the excess of silver nitrate is carried out 
according to Denigés. After Wehrmann’s opinion, this method gives very good results 
and is also easily carried out. He prefers, however, the method given in the Ph. G., 
on account of the limited stability of the N/10 potassium cyanide solution. ; 
After Dirck’s process‘) or its usual modification by Schlicht’), alkaline potassium 
permanganate solution is added to the mustard oil. The excess of permanganate is 
decomposed with alcohol, and the resulting sulphuric acid is determined in the filtrate 
as usual by precipitation with barium chloride, after acidulation with hydrochloric acid 
and the addition of a solution of iodine and potassium iodide until a slight yellow 
coloration results. Instead of potassium permanganate, Haselhoff'*) also employed 
bromine water, thus obtaining better results. 
On checking this test, Wehrmann found very different results. Evidently the 
oxidation of the sulphur is not always quantitative. Wehrmann did not arrive at 
satisfactory results when using bromine water as an oxidizing agent, as bromine does 
not oxidize mustard oil quantitatively, but partly transforms it otherwise. Oily drops 
of dibromo mustard oil, CsH;Brz NCS, separate. This dibromo mustard oil escapes the 
analysis, as it is volatile with steam, and the precipitation of barium sulphate must 
be carried out in the heat, so that Wehrmann found too little mustard oil. | 
1) Zeitschr. Untersuch. d. Nahrungs- u. Genussm. 1 (1898), 235. — 2%) Gildemeister and Hoffmann, loe. cit., 
p. 607. — #8) Gildemeister and Hoffmann, loc. cit., p. 608. — *) Arch. der Pharm. 246 (1908), 58; Report 
April 1908, 69. — 5) Arch. der Pharm, 285 (1897), 58. — §®) Comp. Report April 1911, 129. — 7) Journ. 
de Pharm. et Chim. VI. 15 (1902), 361; Report October 1902, 52. — *) Landw. Versuchs-Stat. 28 (1883), 179. — 
%) Zeitschr. f. anal. Chem. 30 (1891), 661. — 1) Zeitschr. Untersuch. d. Nahrungs- u. Genussm. 1 (1898), 235. 
