120 Mr. Bosanquet on the Illuminating- Power 



The weight of barium carbonate (witherite) used was 



•9976. 



The weight after the passage of dried hydrochloric-acid gas 

 was -9984, 



which shows an increased weight of 



•0008, 

 or a percentage increase in weight of 



•08, 

 whereas the theoretical increase is 14*7 per cent. 



Thus the action of dried hydrochloric-acid gas on witherite 

 is nearly double the amount of its action on Iceland spar. 



The specimen of witherite used was fairly pure, but in 

 performing further experiments on the carbonate of barium 

 the precipitated pure carbonate will be used. Incidentally 

 it was noticed that the dried gas had no action upon cellulose, 

 whereas a moistened filter-paper placed in the current of the 

 gas became rapidly converted into a gum-like mass which 

 was probably hydrocellulose. 



In conclusion, we wish to point out that the variations in 

 weight which we observed were so minute that no definite 

 assertion can be made of an action having taken place ; and 

 the slight variations observed may be due to experimental 

 errors, and to the imprisonment or entanglement of the 

 molecules of hydrochloric-acid gas amongst the finely-divided 

 particles of the Iceland spar or witherite. 



We propose to repeat and extend the investigations on these 

 and other carbonates, using greater weights of the substances 

 experimented upon, longer times of exposure of these sub- 

 stances to the action of the gas, and more elaborate precautions 

 to ensure the absence of moisture. 



XIII. On the Calculation of the Illuminating-Power of 

 Hydrocarbons and their Mixtures* By It. H. M. Bosan- 

 quet, F.R.S.* 



WHILE reading recently the work of Percy Frankland f 

 on the illuminating-power of gases, the following 

 considerations suggested themselves. In considering mix- 

 tures of marsh-gas with ethylene, &c, it is observed by 

 P. Frankland that such mixtures give a greater illuminating 

 effect than mixtures with hydrogen. The marsh-gas is 

 regarded simply as a diluent, and the explanation of its 

 greater power is sought in the greater amount of heat which 



* Communicated by the Author. 

 + Chemical Journal, 1884-85. 



