500 CALCIUM. 



cape of chlorine. The powder or its solution, when heated, or 

 when kept for a considerable time, undergoes decomposition ; 

 18 eq of chlorine, then leaving 17 eq. of chloride of calcium, 

 and 1 eq. of chlorate of lime, and disengaging 12 eq. of oxygen 

 gas, according to the observations of M. Morin. 



CONSTITUTION OF CHLORIDE OF LIME. 



Chloride of lime for bleaching was first prepared by the late 

 Mr. Term ant of Glasgow, who in conjunction with some scien- 

 tific friends, obtained a patent for the manufacture of the dry 

 compound in l*J99. For some time after the true nature of 

 chlorine was known, bleaching powder appears to have been 

 looked upon as simply a combination of chlorine with lime. 

 But more accurate views of combination lead Berzelius to ques- 

 tion the possibility of compounds of elementary bodies with 

 binary compounds, which, if they exist, are certainly exceedingly 

 rare, and to observe the similarity in the absorption of chlorine 

 by lime, with its absorption by a strong solution of potash and 

 the formation of chloric acid, and with the solution of sulphur 

 in alkalies and formation of hyposulphurous acid. He con- 

 cluded that a chlorous acid existed in the bleaching compounds 

 of chlorine, consisting of 1 eq. of chlorine and 3 of oxygen ; the 

 oxygen of this acid being derived from the metallic oxide like 

 that of chloric and hyposulphurous acids, a corresponding 

 quantity of metallic chloride being produced at the same time. 

 This opinion was generally received, the bleaching power of 

 the compound being referred to the facility with which chlorite 

 of lime parts with 4 eq. of oxygen, and becomes chloride of cal- 

 cium. The subsequent discovery by M. Balard, of hypochlo- 

 rous acid, a bleaching compound of chlorine and oxygen, which 

 can be isolated, lent support to the same view, although it al- 

 tered the expression of it, hypochlorous acid being substituted 

 in these compounds for the chlorous, of the separate existence 

 of which there is no evidence. Hypochlorous acid is actually 

 absorbed by hydrate of lime and by solutions of alkalies, with 

 the formation of bleaching compounds, but the identity of these 

 with the compounds resulting from the absorption of chlorine 

 itself is doubtful. The hypochlorous compounds are much less 

 stable than the old chlorides, according to the observations of 

 M. Martens*. 



\nn. dt- f.'h. ft, fie }'h. t. 61, p. 21)3. 



