464 Intelligence and Miscellaneous Articles, 



"6 



and this last term would precisely represent 1 \ atom of sulphuric 

 acid. The hastiness of my experiment could account for a much 

 greater discrepancy. 



This sesquisulphate has no very interesting properties. It ap- 

 pears to be insoluble, but is easily decomposed by cold water. 

 It is usually said that the action of water upon the white biper- 

 sulphate of mercury consists in the resolution of it into the yellow, 

 insoluble, neutral sulphate, and a soluble supersulphate. Yet 

 upon evaporating the liquor thus obtained, I observed the deposition 

 of a white substance resembling in its external characters the biper- 

 sulphate; while the supernatant liquid had those of free sulphuric 

 acid." — Silliman's Journal, vol. xviii. p. 364. 



ON CHLORIDE OF SILVER. BY M. CAVALIER. 



The colour produced in chloride of silver by the action of light has 

 long been known, and a similar change is apparently produced by 

 some chemical reagents, but whether the alterations are identical is a 

 question which M. Cavalier says he does not pretend to decide ; he 

 then states a method by which the violet chloride of silver may be 

 procured without the agency of light : Dissolve some recently pre- 

 pared and perfectly white chloride of silver in ammonia, and pass a 

 current of chlorine gas through it, and the same phaenomenaas occur 

 when the gas is passed through mere solution of ammonia will be 

 presented; such as slight detonation on the arrival of each bubble, 

 abundant white vapours, increase of temperature, and the disengage- 

 ment of azotic gas, &c. Afterwards the solution becomes turbid, 

 and soon a grayish precipitate is observed, and at length it assumes 

 a well marked violet colour ; this colour occurs when the ammonia 

 is completely decomposed by the chlorine. 



What is the nature of this new substance } Is it a smaller or greater 

 quantity of chlorine which has modified the properties of the chloride, 

 or is it identical with the white chloride ; and is the colour acquired 

 merely by a different molecular arrangement? 



The following experiments are in favour of the latter opinion. 



If the violet chloride be dissolved in ammonia, nitric acid precipi- 

 tates it white. Take 20 grains of violet and 20 grains of white chloride, 

 put each into a glass and with them diluted sulphuric acid and a piece 

 of zinc, stirring the chloride with the latter so as to keep it sus- 

 pended ; the chlorides are both decomposed by the hydrogen evolved 

 and metallic silver is obtained, and from each chloride the same quan- 

 tity, viz. 15 grains. 



According to these experiments, the new substance cannot be 

 regarded either as a subchloride or a deutochloride ; every circum- 

 stance seems to prove that the colour is produced merely by a diffe- 

 rent molecular arrangement. In this case it remains to be explained 

 what is the body which forces the chloride to acquire a differentphysical 

 property. The heat produced during the operation has certainly 

 nothing to do with it, for the experiment succeeds equally when the 

 vessel is placed in a freezing mixture. — Journal de Pharmacie, xvi. 

 552. 



Aurora 



