Analysis of Mercury Fulminate (Divers and Kawakita’s Method).—­A weighed quantity of mercury fulminate is added to excess, but measured quantity of fuming hydrochloric acid contained in a retort connected with a receiver holding water.  After heating for some time, the contents of the retort and receiver are mixed and diluted, and the mercury is precipitated by hydrogen sulphide.  By warming and exposure to the air in open vessels the hydrogen sulphide is for the most part dissipated.  The solution is then titrated with potassium hydroxide (KOH), as well as another quantity of hydrochloric acid, equal to that used with the fulminate.  As the mercury chloride is reconverted into hydrochloric acid by the hydrogen sulphide, and as the hydroxylamine does not neutralise to litmus the hydrochloric acid combined with it, there is an equal amount of hydrochloric acid free or available in the two solutions.  Any excess of acid in the one which has received the fulminate will therefore be due to the formic acid generated from the fulminate.  Dr. Divers and M. Kawakita, working by this method, have obtained 31.31 per cent. formic acid, instead of 32.40 required by theory. (Jour.  Chem.  Soc., p. 17, 1884.)

Divers and Kawakita proceed thus:  2.351 grms. dissolved, as already described, in HCl, and afterwards diluted, gave mercury sulphide equal to 70.40 per cent. mercury.  The same solution, after removal of mercury, titrated by iodine for hydroxylamine, gave nitrogen equal to 9.85 per cent., and when evaporated with hydroxyl ammonium chloride equal to 9.55 per cent.  A solution of 2.6665 grms. fulminate in HCl of known amount, after removal of mercury by hydrogen sulphide, gave by titration with potassium hydrate, formic acid equal to 8.17 per cent. of carbon.  Collecting and comparing with calculation from formula we get—­

Calc.  I. II.  III.

Mercury 70.42 70.40 ... ... 
Nitrogen 9.86 9.85 9.55 ... 
Carbon 8.45 ... ... 8.17
Oxygen 11.27 ... ... ...
          _______

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The Analysis of Cap Composition.—­Messrs F.W.  Jones and F.A.  Willcox (Chem.  News, Dec. 11, 1896) have proposed the following process for the analysis of this substance:—­Cap composition usually consists of the ingredients—­potassium chlorate, antimony sulphide, and mercury fulminate, and to estimate these substances in the presence of each other by ordinary analytical methods is a difficult process.  Since the separation of antimony sulphide and mercury fulminate in the presence of potassium chlorate necessitates the treatment of the mixture with hydrochloric acid, and this produces an evolution of hydrogen sulphide from the sulphide, and a consequent precipitation of sulphur; and potassium chlorate cannot be separated from the other ingredients by treatment with water, owing to the appreciable solubility of mercury fulminate in cold water.