1820.] Oxymuriate of Lime. 405 



Subbichloride oflime 48-93 



Muriate of lime 15*46 



Water 27-86 



Uncombined lime and impurity 7-75 



100-00 



The most surprising thing connected with tliis analysis is the 

 very great proportion of water which the bleaching powder 

 contained, amounting to 27-86 per cent. I do not believe that 

 the whole of this quantity could have been present in it when it 

 was originally prepared. The 45-7 grs. of lime which 100 grs. 

 of the bleaching powder contained, supposing it in the state of 

 slacked lime, or hydrate of lime, when originally employed, as it 

 undoubtedly was, would have contained only 10 grs. of water, or 

 little more than one-third of the quantity of water really present 

 in the powder. I am disposed to ascribe this surplus of water 

 to some accidental exposure of the bleaching powder to mois- 

 ture, during a voyage from Belfast, where it was manufactured, 

 to Glasgow, where 1 analyzed it. 



The reader would ob.serve, that besides the oxygen gas, I 

 obtained, during the exposure of the bleaching powder to heat, 

 20-i- cubic inches of azotic gas, or six grains. That the reader 

 may understand the way in which this azotic gas came to be 

 mixed with the oxygen gas, and the correction which must be 

 introduced into the analysis in consequence, it will be necessary 

 to explain how the volume of oxygen gas and of azotic gas was 

 determined. After the process was at an end, the volume of gas 

 extricated was easily determined, as it had been received into 

 glass jars graduated to cubic inches. I merely reduced the 

 volume thus found to what it would have been had the thermo- 

 meter stood at 60°, and the barometer at 30 inches. To deter- 

 mine the volume of common air which was mixed with the 

 oxygen gas thus evolved, the method which I took was this : 

 After the whole apparatus was cold, and the retort with its 

 contents weighed, in order to know the loss of weight which the 

 l)leaching powder had sustained, 1 replaced the retort in the 

 sandpot, and raised the hre to the same intensity as it had been 

 at during the experiment, and I kept it in this state as long as 

 any common air continued to be driven into a graduated glass 

 jar standing over the water trough on purpose to receive it. The 

 volume of air thus driven out of the retort amounted, estimated 

 at the mean temperature and pressure, to 27^V cubic inches. This 

 quantity of consequence was deducted from the volume of gas 

 obtained ; because it is obvious that this volume of common air 

 must have been driven out of the retort by the heat, and that it 

 must have mixed itself with the oxygen gas in the jar. Now 

 27 J- cubic inches of common air are composed of 



