14 ANIMAL CHEMISTRY LECTURE I. 



into three classes, corresponding to the chlorides of the non- 

 metals, by having regard to such considerations as the following : 

 We find that the proportions of the solid non-metals, iodine, 

 sulphur, and phosphorus, which unite with one, two, and three 

 volumes of hydrogen respectively, and with one, two, and three 

 volumes of chlorine, as shown in the previous tables, and which 

 we have agreed to regard as atomic proportions, have their several 

 specific heats expressed approximately by the number 6-3. Now, 

 if we take for the atomic proportions of the different metals those 

 quantities of each of them w'hich have substantially the same 

 specific heat as one another and as the atomic proportions of the 

 solid non-metals, then we find that the chlorides of the metals, like 

 those of the non-metals, must also be divided into monochlorides, 

 di-chlorides, and trichlorides, &c. Accordingly, we have in the 

 opposite table a list of chlorides of metallic and hydrides of non- 

 metallic elements corresponding, you perceive, with one another. 

 (14.) Only a few of these metallic chlorides can be vaporised 

 at manageable temperatures ; but with regard to such of them as 

 are moderately volatile, it is found that two litres of their several 

 vapours contain as many litres of chlorine as are indicated by their 

 respective formulae, deduced from the specific heats of their con- 

 stituent metals. With regard to corrosive sublimate vapour, for 

 instance, we find that from two litres of gaseous chloride of mercury 

 01 2 Hg, we can extract two litres of chlorine, just as we can from the 

 same bulk of chloride of oxygen C1 2 ; whereas, if we take two 

 litres of chloride of bismuth Cl 3 Bi, we can extract therefrom 

 three litres of chlorine, just as we can also extract three litres of 

 chlorine from two litres of chloride of phosphorus C1 3 P. We 

 find, then, that in the case of those metallic chlorides which are 

 volatilisable, we can get from 2 -volumes of their respective 

 vapours, quantities of chlorine identical with the quantities 

 obtainable from similarly formulated non-metallic chlorides. I 

 may take the opportunity of saying that from considerations of 

 this sort, together with others of almost equal cogency, it is de- 

 monstrable that the formula for corrosive sublimate, HgC] 2 , in 

 the old * London Pharmacopoeia ' is right, while that in the new 



