Chemical Science. 237 



uniform stren^h, without involvint^ the trouble of first preparing 

 chlorine gas. For this purpose he has recourse to the mutual 

 action of carbonate of soda and chloride of lime. M. Payen first 

 ascertained the mean proportion of chlorine in the medicinal 

 solutions of M. Labarraque, and then compared it with the pro- 

 portion of chlorine in chloride of lime, represented by 98 degrees 

 of Gay-Lussac's chlorometer. These experiments showed that 

 1 part by weight of chloride of lime of 98° was equivalent to 20 

 parts of medicinal chloride of soda; that 100 parts of this 

 chloride of lime are completely decomposed by 138 parts of crys- 

 tallized sub-carbonate of soda ; and finally, that, by adding 62 

 parts of the last salt to the neutral solution of the chloride, its 

 excess was sufficient to render the compound permanent. The 

 following is therefore the formula for the preparation of the chloride 

 of soda : — 



Chloride of lime at 98° 100 by weight 



Crystallized sub-carbonate of soda 138 „ 



Water 1800 



The chloride of lime is to be dissolved, and the sediment well 

 washed ; carbonate of soda dissolved by heat is to be poured into 

 the solution, the precipitate allowed to subside, the clear fluid 

 decanted, and the solid matter washed on a filter. The collected 

 solutions are neutral chloride of soda ; 62 parts of the sub-carbo- 

 nate of soda are then to be dissolved in the remainder of the water, 

 and added to the preparation; the whole being then filtered, a 

 limpid solution is obtained, indicating 5° by the areometer of 

 Baume. It is the pure chloride of soda. 



If the chloride of lime be of any other strength than 98°, then 

 the relation is easily ascertained by the chlorometer and a brief 

 calculation, and the equivalent of the quantity above directed 

 must be used.— Bull. Philom., 1826, 1.^1. 



20. Mode of Action of Disinfecting Chlorides. — The combinations 

 of chlorine with lime and with the carbonate of soda, have lately 

 been highly recommended as disinfecting agents, and apparently 

 with some reason. The names which have been given to the sub- 

 stances, and the statement of their effects and mode of action 

 have, however, been singularly irregular, vague, and uncertain ; 

 and it is, therefore, with some pleasure we refer to certain experi- 

 ments and observations of a clear and satisfactory nature, by M. 

 Gaultier de Claubry. 



Well-saturated chloride of lime, being dissolved in water, was 

 submitted to the action of a current of carbonic acid gas ; chlorine 

 was quickly disengaged, and by continuing the operation a suffi- 

 cient length of time the whole was expelled; the li()uor no longer 

 possessed bleaching powers, and carbonate of lime had l)een formed 

 and precipitated, except a small portion dissolved by the excess of 

 carbonic acid. 



