448 Notice of some Recent 



Add Salts. — In a memoir by Mitscherlich, it is observed 

 that soda and potash unite in two proportions with sul- 

 phuric acid in order to form acid salts, which may be con- 

 sidered as compounds of hydrous sulphuric acid and neutral 

 salts, as was suggested by Mr. Graham. In well formed 

 crystals we have acid sulphates of potash and soda, in 

 which the sulphuric acid in a hydrous state is in the same 

 proportion as the sulphuric acid in the neutral salts ; then 

 an acid sulphate of soda NO, SO^ + ^ HO, SO^ and lastly 

 a sulphate of potash, in which the hydrous acid is only the 

 4th of the sulphuric acid of the neutral salts. Ammonia 

 unites with sulphuric acid (NH^ HO, SO^ + ^ HO, SO^) 

 as potash does with manganic acid, (KO, MnO^ + -J HO 

 MnO^) but only in a proportion to form an acid salt. The 

 acid salts of chromic acid, are on the contrary, only com- 

 pounds of chromic acid and a base ; the acid chromate of 

 potash contains in the same quantity of base twice as much 

 as another acid salt, which is obtained by dissolving the 

 first acid salt in nitric acid, and collecting the crystals pre- 

 cipitated in the solution. The acid seleniate of potash 

 (KO Se O^ + HO, Se O^) has the same form as the cor- 

 responding acid sulphate. The acid sulphate of potash has 

 the same form as sulphur ; after being fused it assumes 

 a form similar to that assumed by melted sulphur. The 

 acid manganate of potash and sulphate of ammonia have 

 the same form and composition.^ 



Decomposition of Iodide of Mercury by Light. — The iodide 

 of mercury, when dried in the light of the sun, becomes 

 dark olive coloured. According to Artus, there is no free 

 iodine separated ; but hydriodic acid is given out, so that 

 the combination, formed by the light, consists of protoxide 

 of mercury and iodide. Water must, therefore, be neces- 

 sarily present. Iodide of mercury dried in the water bath 

 is, however, almost indifferent to light.f 



Preparation of Antimony free from Arsenic. — According 

 to Artus, this may be effected as follows : mix one part of 

 finely powdered crude antimony with two parts of common 

 salt. Digest the mixture in a retort with five parts con- 

 centrated sulphuric acid and two parts water for six or 

 eight hours; boil it then for one hour; dilute the solution 

 with an equal volume of rectified spirit of wine, or with as 



* L*Institut,170. t Journ. fiir prakt Chemie, viii. 6^. 



