402 Dr. Thomson on [June, 



we see also what has become of the oxygen of the oxide of 

 silver. One portion of the silver is reduced to the metallic state, 

 and precipitates in combination with the chlorine ; while anothei* 

 portion remaining in the state of oxide unites witli chloric 

 acid, into which a portion of the chlorine has been changed; and 

 the chlorate of silver thus formed remains in solution in the 

 liquid. It is easy to see how much of the chlorine is precipi- 

 tated in this case, and how much of it is converted into chloric 

 acid. Five-sixths of the silver must be reduced to the metallic 

 state, and unite with chlorine ; the remaining sixth will continue 

 in the state of oxide, and will unite with one-sixth of the chlo- 

 rine, which has been converted into chloric acid by uniting with 

 five atoms of oxygen given out by the reduced silver. Thus it 

 appears that when chloride of lime is analyzed by means of 

 nitrate of silver, one-sixth of the chlorine is converted into chlo- 

 ric acid, and escapes detection. 



I have, therefore, had recourse to the following method of 

 analyzing chloride of lime, which I consider as accurate, and as 

 attended with fully as little diflSculty as the method which I 

 employed formerly. My experiments were made upon a very 

 large scale ; but it is obvious that the scale might be very much 

 diminished, without injuring the accuracy of the results. 



2714 grains of bleaching powder recently prepared, but very 

 moist, were put into a retort, the weight of which had been pre- 

 viously ascertained, and marked upon the glass with a diamond. 

 To the beak of the retort was luted a bent tube to convey any 

 gaseous products into glass jars standing upon the shelf of the 

 water trough. The retort was put into the sandpot of a furnace, 

 and was gradually heated nearly to redness, and kept at that 

 temperature till all the gaseous products ceased to come over. 

 During this process, which lasted about four hours, there were 

 extricated the following gases : 



Oxygen gas 333"48 cubic inches. 



Azoti*> gas 20-33 



corrected to the mean pressure and temperature. 



Grains. 



Now 333*48 cubic inches of oxygen gas weigh 113-00 

 20-33 cubic inches of azotic gas weigh.. 6-02 



Total weight 119-02 



The lost of weight sustained by the bleaching powder amounted 

 to 875 grs. ; consequently the water driven oft' from the powder 

 by the distillation amounted to 755-98 grs. 



I presume that the reader is aware that it is already known 

 that the bleaching powder is a combination of chlorine and lime, 

 or a chloride of lime. I suppose him aware also that when lime 

 is heated to redness, and a current of chlorine passed through it. 



