286 Prof. Tyndall on the Absorption and 



Table III. 



Tensions. 



i i ■ . — » .... j 



Name of substance. 0*1 inch. 0- 5 inch. TO inch. 



Bisulphide of carbon ... 15 47 62 



Iodide of methyle .... 35 147 242 



Benzole 66 182 267 



Chloroform 85 182 236 



Methylic alcohol .... 109 390 590 



Iodide of ethyle 158 290 390 



Amylene 182 535 823 



Sulphuric ether 300 710 870 



Alcohol 325 622 



Formic ether ...... 480 870 1075 



Acetic ether 590 980 1195 



Propionate of ethyle . . . 596 970 



Boracic ether 620 



Let us compare some of the results of this Table of trans- 

 parent vapours with the action of the highly coloured vapour of 

 bromine. The absorption of bromine vapour at 1 inch tension 

 is about 6, and at 0*1 of an inch tension would probably not 

 exceed 1 ; hence at 0*1 of an inch tension, bisulphide of carbon 

 has probably 15 times the absorbent power of bromine; but 

 bisulphide of carbon is the feeblest of the compound vapours 

 that I have yet discovered. The strongest of these, boracic 

 ether, has, according to the above estimate, and at the tension 

 stated, more than 600 times the absorbing energy of the strongly 

 coloured bromine. 



The whole of the numbers in the above Table are referred to 

 atmospheric air as unity; 0*1 of an inch of bisulphide-of-carbon 

 vapour, for example, absorbs 15 times as much as a whole 

 atmosphere of air. Let us compare, for an instant, the action 

 of boracic ether with that of air. We arrive at an approximate 

 comparison in this way. The absorption of the tenth of an inch 

 of boracic ether is something more than that of a whole inch of 

 methylic alcohol ; by diminishing the quantity of methylic alcohol 

 to one-tenth, we reduce its absorption from 590 to 109. The 

 absorption of one-tenth of an inch of boracic ether is 620°; 

 suppose it to diminish in the proportion above found for me- 

 thylic alcohol, we should have for 0*01 of an inch of boracic 

 ether an absorption of 111; that is to say, for ^oVo^h of an 

 atmosphere of boracic ether, we should have an absorption 111 

 times that of a whole atmosphere of oxygen, nitrogen, and hy- 

 drogen, or atmospheric air. 



With the transparent elementary gases it is impossible to 

 measure directly the absorption of O'l of an inch; but assuming, 



