FAVRE AND SILBERMA NN ' S CALORIMETER. 2J 



In this example the corrections are not very important, 

 since they do not exceed one-half per cent. These are the 

 ordinary conditions when the coal used is in pieces. With 

 pulverized coal, on the contrary, the quantity of unburnt 

 carbon and of combustible gases increases considerably and 

 renders results less certain. The oppor- 

 tunity we have to weigh the cinders of 

 each test obviates pulverization of the coal 

 to obtain an average sample of the cinders. 



Favre and Silbermann's calorimeter has 

 been modified by Berthelot in several par- 

 ticulars.* He has happily modified the 

 agitator and given it a coiled form, as 

 shown in Fig. 5, a detailed description of 

 which is given in his Essai de Me'canique 

 Chimique, p. 145. 



This agitator has the advantage over 

 the old one of more completely mixing 

 the water, with less force, and without 

 accelerating evaporation. Fig. 5 shows 

 it placed in the middle of the calorimeter. 



FIG. 5. 



He has also replaced the gold-plated copper combustion- 

 chamber by the glass apparatus which Alexejew used for 

 combustibles. 



*The F. & S. calorimeter with all accessories and an agitator (not me- 

 chanical) costs about 500 francs ($100.00); with mechanical agitator arranged 

 for a laboratory turbine or dynamo the cost is about 600 francs ($120.00). 

 Berthelot's calorimetric bomb of platinum, enamelled inside and not 

 double, costs no more, and is much preferable. A single operator can 

 handle it, while the F. & S. apparatus requires two. 



Nevertheless, the manner of working the F. & S. calorimeter is de- 

 scribed in detail, because its use is surrounded by conditions easily realized 

 in all .countries. The calorimetric bomb requires oxygen compressed to 25 

 atmospheres, which cannot be obtained everywhere. 



