a Nexo Class of Salts. 273 



phuric acid, crystals are formed and may be separated ; they 

 must be dried over sulphuric acid, as they are exceedingly 

 deliquescent. These crystals belong to the oblique system, 

 but on account of their excessive tendency to deliquesce, it is 

 difficult to measure their angles with accordant results. The 

 angles between normals to the only faces which gave re- 

 sults to be depended on, are stated by Prof. Miller to be as 

 follows : — 



It will be seen that the equality of the angles ec and g'c' is a 

 tolerably certain indication that the crystals belong to the ob- 

 lique system. 



The acid made by the action of hydrochloric acid on nitro- 

 prusside of siver, and evaporated over sulphuric acid in the 

 cold, crystallized (light being excluded) without the deposition 

 of oxide of iron, but the smell of hydrocyanic acid, accom- 

 panied by a peculiar pungent smell, was strongly perceptible. 

 Analysis shows that these crystals are the same as those ob- 

 tained from a boiled solution. 



Properties of the Crystallized Acid. — The crystallized acid 

 is of a dark red colour, and has a very acid reaction, the cry- 

 stals being generally flattened and of tolerable size. They are 

 quite as deliquescent as chloride of calcium. They dissolve 

 to a large extent in water, and are also soluble in alcohol and 

 in aether. They may be dried in the water-bath without 

 change, but their aqueous solution cannot be boiled without 

 decomposition. 



The following analyses were made on crystals obtained from 

 a boiled solution, and were dried at 212°. The acid was that 

 made by the action of hydrochloric acid on the silver salt. 

 Nos. I. II. and III. were preparations made at distinct times. 



The iron was determined by calcination and by treating the 

 residual oxide with nitrate of ammonia. 



I. 2*345 grs. gave 0*800 gr. peroxide of iron. 



II. 3*915 grs. gave 1*325 gr. peroxide of iron. 



III. 3*580 grs. gave 1*220 gr. peroxide of iron. 



The combustions were made in the usual way. 



I. 7'720 grs. gave 7*005 grs. CO^ and 1-175 gr. HO. 

 II. 10*810 grs. gave 9*880 grs. CO^^ and 1*665 gr. HO. 

 III. 4*385 grs. gave 3*980 grs. CO^ and 0*700 gr. HO. 

 An estimation of nitrogen by Bunsen's method gave the 

 following result : — 



