OF ARTS AND SCIENCES. 93 



traces, until the disulphide with the dissolved iodide of antimony was 

 exposed to the direct sun-rays for a long time, as above described. An 

 equal amount of exposure before dissolving the iodide had no apparent 

 effect. Again, after finding that iodide of antimony dissolved in disul- 

 phide of carbon is oxidized by ozonized air even in the dark, we 

 sought to determine whether the monoclinic crystals were formed under 

 ■these conditions independent of the action of the light ; and, to this 

 question also, our experiments returned a negative answer. 



The production of the monoclinic crystals appears, therefore, to be 

 independent of the oxidation of the iodide of antimony ; although, 

 like the latter, it is also due to the action of the sunlight. The effect 

 seems to depend on a change produced in the solvent by the sun's rays, 

 probably the same partial reduction of the carbonic disulphide which 

 has been studied by O. Loew.* At least, it is certain that the mono- 

 clinic crystals contain a small amount of carbonaceous impurity, which 

 they acquire from the solvent ; and our theory is, tliat, under the action 

 of the light, the crystalline molecules become as it were loaded by the 

 adhesion of this material, and that the monoclinic habit is due to this 

 circumstance. It may be mentioned, in this connection, that when the 

 monoclinic crystals are redissolved in carbonic disulphide, and recrys- 

 tallized, only a small part of the material, as a rule, retains the mon- 

 clinic form, the rest appearing in the more stable hexagonal condition. 

 Still, there is a certain persistency of the new condition which would 

 be natural with such a molecular adhesion as our theory assumes ; and 

 the remarkable adhesiveness of the material which is deposited by 

 disulphide of carbon under the influence of the light is worthy of notice 

 in this connection. Other facts bearing on this theory can be more 

 intelligently discussed after this new form has been described. 



The specific gravity of the monoclinic iodide of antimony was deter- 

 mined in the same way as that of the hexagonal modification (page 

 83), and with the following results : — 



Specific Gravity of Monoclinic Antimonious Iodide. 



No. "Weight taken. Sp. Gr. at 22°. 



1. 1.2434 4.786 



2. 2.2605 4.750 



Mean value 4.768 



*Am. Journal of Science (2), xlvi. 363, and xli. 251. 



