4 Dr. Uit' on C/tl<»'i(h' of Lime. 



whole, however, I prefer the green sulphate test for precision*." 

 But oxymuriate of lime is a compound not very soluble in wa- 

 ter, as we shall afterwards see ; and therefore it will be imper- 

 fectly taken up by " a small quantity of water." The plan, 

 however, of separating the chlorine by an acid, is good, and, 

 when practised in a particular way, which will be described in 

 the sequel, affords the best and readiest mode of analysis. As 

 to his preference of the copperas test, I can only say that Mr. 

 Dalton's olfactory nerves are more tractable than mine. On 

 the whole, we must regard these two papers as highly creditable 

 to this celebrated chemist. His methods of research display 

 his characteristic ingenuity, and his conclusions are such, that 

 subsequent investigators have been content to repeat them as 

 their own. 



The next occasion on which I find the subject of chloride of 

 lime discussed, is in the Annales de Chimie et de Physique, for 

 April 1818, where we meet with a good practical paper, by 

 J. J.Welter. His mode of examination was, to try how much of 

 a dilute solution of indigo, in sulphuric acid, could be deprived 

 of its colour by a certain weight of a saturated chloride of 

 lime ; and knowing, by previous experiments, the quantity of 

 chlorine adequate to the same effect, he thence could infer the 

 quantity of chlorine condensed in the hydrate of lime. From 

 these experiments, which seem to have been conducted with as 

 much precision as the method of discoloration admits, he con- 

 cludes that the saturated combination of lime with chlorine, is 

 a demi-chloride ; that is, a compound of 46.78 (an atom of 

 hydrate of lime) -|- till =22.05, (half a proportion of chlorine). 

 By the same means he is led to infer, that, when lime or potash 

 is added to water impregnated with a known quantity of chlo- 

 rine, the resulting chloride is free from chlorate, because as 

 much indigo colour is destroyed by it as the free chlorine could 

 have done. " On pouring water on the above demi-chloride," 

 says M. Welter, ' a partition takes place ; the water dissolves 

 all the chlorine along with some lime, and what remains is the 



* Annals of Philos. II. p, 7. 



