^4 Dr. Thomson on [June, 



We have seen that the chlorine contained in the bleaching salt 

 weighed 508*557 grs. Now if we suppose this chlorine to be 

 converted into muriatic acid, it would increase in the proportion 

 of 4-5 : 4-626 ; so that it would become 522*684 grs. Thus the 

 muriatic acid which was extracted from the bleaching powder 

 exceeds that which would have been formed by the conversion 

 of the chlorine into muriatic acid by (757-973 — 522-684 =) 

 235*289 grs. This quantity must have existed iia the bleaching 

 powder in the state of muriatic acid, and it must have been in 

 combination with lime. Now 235*289 grs. of muriatic acid 

 require for saturation 184-4 grs. of lime ; consequently the 

 bleaching powder contained 419*689 grs. of muriate of lima, 

 equivalent to 362*46 grs. of chloride of calcium. 



It was first demonstrated by Mr. Dalton, and has since been 

 amply confirmed by my own experiments, and by those of other 

 chemists, that bleaching powder (supposing it pure) is a com- 

 pound of one atom chlorine + two atoms lime. Now the chlo- 

 rine contained in the bleaching powder weighed 508*557 grs. 

 and it was combined with (594*0862 - 184*4) x 2 = 819*3724 

 grs. of lime. This agrees very nearly with the theoretical num- 

 ber, which is 818*4538. 



From the preceding analysis, it appears that the 2714 grs. of 

 bleaching powder, subjected to analysis, contained the following 

 ingredients : 



Subbichloride of lime 1327*9294 



Water 755*9800 



Muriate of lime 419*6890 



2503*5984 

 Loss 210*4016 



Total 2714*0000 



This loss was found among the residue which remained on the 

 filter when the liquid containing the muriate of lime was sepa- 

 rated from the undissolved portion. This undissolved portion 

 weighed 697*6 grs. It contained, however, half the lime that 

 had been united to the chlorine, and which we have seen above 

 amounted to 409*6862 grs. ; so that there appears to be a surplus 

 amounting to 77*5122 grs. *. but this was owing to the lime 

 having absorbed carbonic acid while drying in the open air. 

 Accordingly 100 grains of this residue being dissolved in nitric 

 acid lost 11*5 grs. in weight, so that the whole would have lost 

 80'224 grs. which comes within 2^ grs. of the surplus. 



On analyzing this white powder on the filter, I found it to be 

 a mixture of quicklime, carbonate of lime, and a little clayey 

 matter, with which the lime no doubt had been contaminated. 

 If we reduce the substances found by the preceding analysis to 

 100 parts, we shall obtain the composition of our bleaching 

 powder as follows : 



