72 Faraday on Hydrate of Chlorine. 



and that the dry gas could not be condensed at a temperature 

 equal even to — 40° Fahr., whilst, on the contrary, moist gas, or 

 a solution of chlorine in water, crystallized at the temperature 

 of 40° Fahr. 



M. Thenard, in his Traite de Chimie, has described the depo- 

 sition of the hydrate of chlorine by cold from an aqueous solu- 

 tion of the gas. It forms crystals of a bright yellow colour, 

 which liquefy when their temperature is slightly raised, and in 

 so doing give off" abundance of gas. 



This substance may be obtained well crystallized, by intro- 

 ducing into a clean bottle of the gas, a little water, but not 

 sufficient to convert the whole into hydrate, and then placing 

 the bottle in a situation the temperature of which is about or 

 below freezing, for a few days : and I have constantly found 

 the crystals better formed in the dark than in the light. 

 The hydrate is produced in a crust or in dendritical cry^ 

 stals ; but being left to itself, will in a few days sublime 

 from one part of the bottle to another in the manner of cam- 

 phor, and form brilliant and comparatively large erystals. 

 These are of a bright yellow colour, and sometimes, though 

 rarely, are delicate prismatic needles extending from half an 

 inch to two inches into the atmosphere of the bottle : gene- 

 rally they are of shorter formg, and when most perfect an.d 

 simple, have appeared to me to be acute flattened octoedra, the 

 three axes of the octoedron having different dimensions. 



Though a solution of chlorine deposits the hydrate when 

 cooled, yet a portion remains in solution, and the crystals, also 

 dissolve slowly in water. It is, therefore, soluble, though not 

 so much so as chlorine gas. When a solution of chlorine is 

 cooled gradually till the whole is frozen, there is a perfect sepa- 

 ration of the hydrate of chlorine from the rest of the water, or 

 rather from the ice ; for crystals of ice, formed in a solution oj;' 

 chlorine, when washed in pure water, and then dissolved, do 

 not trouble nitrate of silver. 



I neglected to ascertain the specific gravity of the crystals 

 whilst the weather was cold and they were readily obtainable ; 

 but, I have endeavoured since to do so by means of cooling 



