'tSO Dr. Dalton's Observations on certain Liquids 



\voocl may be taken for an example: by this process we find a 

 solid body resolved into another solid body, charcoal ; into 

 various liquids, as water, acetic acid, and pyroxylic spirit ; 

 into gases, as carbonic acid, carburetted hydrogen, carbonic 

 oxide, and hydrogen. Caoutchouc is highly combustible: 

 when we burn a slip of it, the flame is white and brilliant ; and 

 if we extinguish the flame suddenly, the heated extremity is 

 soft and nearly fluid ; hence it would appear that this substance 

 is reducible to a fluid before decomposition, and in that state 

 might probably be distilled like the fat oils ; but, like these, 

 the products of the first, second, and future distillations would 

 be successively more volatile, and require a lower temperature 

 for their distillation. This it seems has been found to be the 

 fact. 



Having been favoured by an unknown friend with four phials 

 of liquids obtained from caoutchouc by successive distillations 

 (as I apprehend), 1 found 



the 1st, a deep-coloured liquid, marked sp.gr '86; 



Snd, a slightly coloured liquid, marked ... '837; 



3rd, a colourless liquid, marked -752; 



4th, a colourless licjuid, marked '680; 



all of which specific gravities I found very nearly correct. 

 The last, I believe, is lighter than any other known liquid, ex- 

 cept perhaps the one mentioned by Dr. Faraday, — see Phil. 

 Trans. 1825, page 452. 



The 1st liquid I did not find the boiling-point of, but it is 

 higher than any of the following: 



the 2nd boils at about 290° or 300° ; 



3rd -T 140°; 



4th 107° or 108°. 



By letting a small portion of the 4th liquor through the 

 mercury in a barometer tube, 1 find the force of its vapour in 

 vacuo is very nearly die same as that of sulphuric aether. The 

 other three liquors I did not expose in the same way, because 

 it is obvious, from their boiling-points, that their elasticities in 

 vacuo must be much inferior to that of the 4th. 



In order to form some estimate of the relative evaporation 

 of the four liquids, I poured out small portions of the several 

 liquids into glass cups, and dipped the bulb of a thermometer 

 into the liquids, withdrawing it immediately to notice the re- 

 duction of temperature by the evaporation. The thermometer 

 being at the temperature of the room, 69°, it was cooled 



15° by four or five successive dips into the liquor No. 4, 



8° by dips into No. 3, 



1^° by dips into No. 2, 



2° by dips into No. 1, 



