Sulphuric acid = 67.20 per cent. |
Nitric acid = 11.07 " |- Specific gravity = 1.7075.
Water = 12.73 " |
This method is accurate enough for general use in the nitric acid factory. The acid mixture may be taken by volume for determining nitric oxide in nitrometer. Two c.c. is a convenient quantity in the above case, then 2 x 1.7075 (specific gravity) = 3.414 grms. taken, gave 145 c.c. NO (barometer = 748 mm, and temperature = 15°C.) equals 134.9 c.c. (corr.) and as 1 c.c. NO = .0282 grm. HNO_{3} 135 x .0282 = .378 grm. = 11.07 per cent. nitric acid.
~Sodium Nitrate.~ Determine moisture and chlorine by the usual methods, and the total, NaNO_{3}, by means of nitrometer—0.45 grm. is a very convenient quantity to work on (gives about 123 c.c. gas); grind very fine, and dissolve in a very little hot water in the cup of the nitrometer; use about 15 c.c. concentrated H_{2}SO_{4}. One cubic cent. of NO equals .003805 grm. of NaNO_{3}. The insoluble matter, both organic and inorganic, should also be determined, also sulphate of soda and lime tested for.
~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 … … …
_______
100.00
~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.
In the course of some experiments on the solubility of mercury fulminate Messrs Jones and Willcox observed that this body was readily soluble in acetone and other ethereal solvents when they were saturated with ammonia gas, and that chlorate of potash and sulphide of antimony were insoluble in pure acetone saturated with ammonia; these observations at once afforded a simple method of separating the three ingredients of cap composition. By employing this solution of acetone and ammonia an analysis can be made in a comparatively short time, and yields results of sufficient accuracy for all technical purposes. The following are the details of the process:—