EXPERIMENTAL DETAILS. 



247 



(8) The parts being all adjusted, the air is exhausted in the 

 bell glass by means of an inverted syphon. 



(9) Then we have merely to follow the progress of the 

 thermometer, 0, for ten minutes. 



(10) We then heat and finally melt the little platinum wire 

 by means of a current of four Bunsen elements, the hydroxy- 

 lamine hydrochloride falls into the potash and is immediately 

 destroyed. The gases produced by its destruction are given 

 off under the bell glass. We give this glass a rotatory move- 

 ment for a few minutes by means of the rod S, taking care to 

 keep it completely submerged. Headings of the 

 thermometer are taken every minute. 



(11) This done, we break the bottom of the 

 large glass tube by means of a- platinum crusher 

 introduced from outside and fixed at the ex- 

 tremity of a long rod of the same metal (Fig. 43) ; 

 the liquids and other substances contained in the 

 tubes spread out into the calorimeter and remain 

 in it completely intermingled, this being effected 

 by a suitable agitation which is easily performed 

 by means of the rod S. 



(12) During this interval, and for a little while 

 after, the progress of the thermometer is followed ; 

 all the thermal data are thus determined. 



(13) This being done, all that remains is to 

 know the volume of nitrogen developed by the 

 decomposition. For this purpose we put the 

 platinum calorimeter with the bell glass into 

 the water contained in a very large earthen pan, 

 so as completely to submerge them. The bell 

 glass is then raised, so as to render it independent 

 of the calorimeter, and the gases are transferred 

 to a graduated testing apparatus. 



These gases contain the nitrogen given off Fig. 43. Plati- 

 (mixed with three or four per cent, of nitrogen num crusher, 

 monoxide, according to the analyses), plus the 

 air contained at first in the large tube and in the liberating 

 tube. The volume of this air is known by the previous gauging 

 of the tubes, if we deduct the liquid volumes of the potash 

 and the various other objects introduced into the tube for the 

 experiment. These volumes having been each measured sepa- 

 rately, we succeed, finally, in ascertaining within about half 

 a cubic centimetre the volume of nitrogen given off by the 

 destruction of the hydroxylamine. 



In the author's experiments this volume corresponded to 

 78 and 79 per cent, of the weight of the salt subjected to the 

 reaction. The surplus of the salt, or more correctly the surplus 

 of the hydroxylamine derived from it, is found unaltered in the 



