322 M. C. Lea — Silver Hemisuljihate. 



Art. XLI. — On Silver Hemisitlphate ; by M. Carey Lea. 



The existence of those substances which I described some 

 years ago under the name of photosalts of silver* necessarily 

 implied the existence of the hemihaloids of silver also, as 

 these latter .entered into the composition of the photosalts. 

 Similar inferences, though less definite, had long been drawn 

 from the action of light on silver haloids. Two of these, the 

 chloride and bromide, lost by the action of light their com- 

 plete solubility in ammonia without becoming completely sol- 

 uble in nitric acid. Evidently there was indicated an inter- 

 mediate compound between the normal haloid and metallic 

 silver. During the last ten or twelve years I have devoted 

 much time to the attempt to isolate these lower compounds of 

 silver and to gain some certain knowledge as to the hemioxide, 

 whose existence seemed almost a necessary inference from that 

 of the hemihaloids. Some eight years ago, I obtained a sub- 

 stance having all the properties which one would be disposed 

 to ascribe to Ag 2 Cl and a large number of analyses made 

 seemed to confirm the view. I hesitated, however, to publish 

 a description of it, not feeling entire certainty that it might 

 not be a mixture, as to which a concordance of the proportions 

 found of Ag and CI with theory gives no sufficient informa- 

 tion. Since then M. Guntz has described a subchloride ob- 

 tained by acting on silver hemifluoride with phosphorus penta- 

 chloride and a hemioxide derived from it. Up to the present 

 time no combination of silver hemioxide with an oxyacid has 

 been known. 



Such a combination I have been able to obtain as a double 

 salt of hemisulphate and normal sulphate containing one mole- 

 cule of each. The new salt has a light bright brown color, and 

 exhibits a stability which in view of its composition, is some- 

 thing remarkable. It has no tendency either to oxidation or 

 to reduction. Nitric acid, unless very strong, has but little 

 action upon it. Acid of 1*42 poured over it in large excess 

 and let stand for several days gradually dissolves it completely, 

 but the same acid diluted with with two or three times its vol- 

 ume of water has so little action that it forms a convenient 

 means of purification. On the other hand, ferrous sulphate 

 which instantly reduces argentic sulphate has no action what- 

 ever on the new substance even with several days' contact 

 Hot strong sulphuric acid has no action. It might almost be 

 expected that under its influence, the argentous salt would 

 gradually take up oxygen and be converted into argentic sul- 



* This Journal, xxxiii, May and June. 1887. 



