456 



Mr. W. Rosenhain on an 



of coal were used to render the measurements more exact ; 

 when the combustion itself was over, the sample was in each 

 case removed from the calorimeter without having been 

 brought into contact with the calorimeter-water ; this 

 " calorimeter ash " was then dried to constant weight at 

 ISO 3 C, and its weight determined ; it was then exposed to 

 oxidation in a muffle, also until constant weight was attained; 

 the difference between the weight before and after the treat- 

 ment in the muffle was taken to represent the weight of the 

 unburnt residue left by the combustion in the calorimeter, 

 and, as the following table will serve to show, this was in all 

 cases found to be small. 



Weight of 

 coal used. 



Ash from 

 calorimeter. 



Ash after Difference 

 muffle. (unburnt). 



Percentage of 

 "unburnt residue." 



2-6019 

 3-4228 



2-5023 

 1-7865 



•3651 



•4854 

 •3420 



•2848 



•3572 -0079 

 •4790 -0064 

 •3341 -0079 

 •2791 -0057 



•30 per cent. 

 •19 „ 

 •31 „ 



•32 „ 



It has also been suggested that in the present form of 

 instrument there is a risk of a small quantity of carbon mon- 

 oxide being formed and escaping unburnt in the gases 

 leaving the calorimeter. To test this point the author made 

 a number of analyses of the gases leaving the calorimeter 

 during a combustion. For this purpose the valve in the 

 base of the instrument was firmly screwed down by means of 

 a piece of india rubber packing, and the plug in the opening 

 of the lower outlet-tube was rep'aced by a glass tube. The 

 gases, therefore, instead of bubbling up through the water of 

 the calorimeter, passed along this tube and through the 

 apparatus arranged for the analysis. The gases were first 

 passed through solutions of caustic potash, to absorb the 

 carbon dioxide, and then through strong sulphuric acid ; the 

 only gases which would pass through would be oxygen and 

 any carbonic oxide present ; this mixture was then passed 

 through a long tube filled with palladium asbestos, and kept 

 hot during the experiment. Any monoxide present would 

 be oxidized, and its presence and amount observed by the 

 increase in weight of the soda-lime ab-orption-tubes through 

 which the gases were passed after again drying them. As 

 the entire arrangement was in action before the specimen 

 was ignited, it will be seen that all the gases passed through 

 the apparatus, so that any formation of carbon monoxide, even 

 at the beginning or end of the combustion, would be detected. 



