M. C. Lea — Silver Hemisulphate. 329 



be obtained. But tbe action of tbe hypophosphite tends so 

 strongly to carry the reaction still further that reduced silver 

 appears, and in removing this with nitric acid the double salt 

 results. A confirmation of this is found in the fact that the 

 treatment with nitric acid much reduces the deep terra cotta 

 color of the original product. If this difficulty can be over- 

 come we may yet obtain hemisalt isolated. 



There is reason to suppose that numerous other compounds 

 of silver hemioxide with oxyacids may exist. These com- 

 pounds cannot be obtained by acting on the normal salts with 

 sodium hypophosphite or with hypophosphorous acid, but it 

 appears probable that they may be produced when the normal 

 salts are formed in the presence of sodium hypophosphite. 

 If to the last named salt we add a solution of a salt capable of 

 precipitating silver nitrate, and then further add silver nitrate, 

 we obtain precipitates which after standing some hours with 

 frequent stirring appear to contain compounds of silver hemi- 

 oxide. But these products do not resist the action of nitric? 

 acid ; consequently there appears to be no means of purifying 

 them and of deciding with certainty as to their nature. 



When sodium citrate and hypophosphite are dissolved 

 together and a little silver nitrate added to get rid of chlo- 

 rides, then after standing and filtering more silver nitrate is 

 added, a precipitate is obtained which after a time appears to 

 contain silver hemicitrate in an impure form. When a little 

 of this precipitate is put into much water containing a trace of 

 ammonia (five or six drops to 100 c. c), a fine rose-red solution 

 results. 



Most oxysalts of silver are darkened by light. In a paper 

 published in this Journal for* July, 1887, I mentioned that 

 films of these salts exposed to light and then treated with 

 dilute hydrochloric or hydrobromic acid appeared to be con- 

 verted into hemichloride or hemibromide, and argued there- 

 from that oxyacid hemisalts of silver must exist, and be 

 formed by action of light on normal salts. I believe that I 

 have been able to prove the existence of a hemisulphate with 

 a strong probability that many other hemisalts may be formed 

 both by the action of light and also by purely chemical means. 

 It is possible that at some future time we may succeed in 

 obtaining some of these compounds in a state of purity. 



