M. Carey Lea — AHotropio Forms of Silver. 485 



animation of its absorption spectrum showed it to be still a 

 true solution. From this solution the silver was first removed 

 by H 2 S and then the citric acid was determined in the above 

 described way. (If the silver were thrown down by hydro- 

 chloric acid, the reliability of the citric determination would 

 be impaired.) Next, the silver sulphide was converted into 

 chloride and weighed. The result gave the ratio 



1 gram silver to "03195 gram citric acid. 



In this case washing out the sulphates, etc., was an affair of 

 several days. The work was repeated, reducing the time as 

 much as possible. The material was precipitated, decanted as 

 soon as settled, thrown upon a filter pump and the funnel kept 

 constantly full of amnionic nitrate in dilute solution by a wash 

 bottle. By using very thick paper and a powerful pressure 

 the entire washing was rapidly finished so that in about six 

 hours from first precipitation the material was thoroughly 

 washed, redissolved and again filtered and placed under the 

 action of H 2 S. The result was 



1 gram silver to •0130 citric acid. 



When these relations are reduced from weights to equiva- 

 lents, they become : 



No. 1, 1 equiv. citric acid to 55*63 equivs. silver. 

 No. 2, 1 " " 193-7 " 



indicating both that the proportion of citric acid present is 

 variable and that it is certainly not in stoichiometrical combi- 

 nation with the silver in the substance examined. 



It has been already said that these solutions before being 

 acted upon by H 2 S were examined optically and found to be 

 true solutions. The inference therefore seems to be very 

 strong that there exists an allotropic form of silver freely 

 soluble in water. This is a property so exceptional in a metal 

 that I have admitted it with much hesitation. The principal 

 arguments are as follows : 



The content of silver in the various products was very care- 

 fully, and I believe I may say quite accurately, determined : it 

 was extremely high, always above 97 per cent. As already 

 remarked, this virtually excludes the presence of all elements 

 except hydrogen and possibly oxygen. These elements were 

 carefully searched for, but their presence could not be detected. 

 To suppose that we had to do with a mixture in which some 

 compound of silver was mixed with metallic silver was not 

 possible, for as the whole was soluble we should still have to 

 admit the solubility of silver. 



"We have consequently to deal with a substance containing 

 over 97 per cent of silver, and neither hydrogen nor oxygen in 



