Minerals of Organic Origin. No. V. Elastic Bitumen, 23 



The loss may either be due to the presence of oxygen, or 

 to the extraction of a trace of the more volatile part when 

 heated, before burning, for the purpose of pumping out the 

 water. 



2. The second, of which I had a larger supply, had a close 

 resemblance to moderately soft India rubber. Its colour was 

 of a darker brown. Boiled in water its colour became paler, 

 but it again darkened on drying at 212°. During the boiling 

 a more volatile portion collected on the surface of the water 

 and the sides of the flask, which on cooling presented the ap- 

 pearance of a very soft white, or slightly brownish solid. At 

 212° in the air it also diminished in weight. Boiling alcohol 

 and aether extracted from it a similar volatile substance, but 

 very sparingly, and of a browner colour. I did not recognise 

 in this substance the bitter taste remarked by M. Henry. I 

 have in my possession, however, a substance of a similar kind 

 from South America, which I shall describe in a future Num- 

 ber, possessed of an intensely bitter taste, a trace of which 

 may, perhaps, be occasionally present in the elastic bitu- 

 men, and give a bitterness to the matter extracted from it by 

 aether. 



Of this second or harder variety, 13*66 grs., cut into small 

 pieces and boiled once in aether and three times in alcohol, 

 lost 2*46, or 1 8*008 per cent. It still retained its elasticity 

 after this treatment. 



Of the portion thus boiled, 11*195 grs. gave on burning 

 34*165 grs. of carbonic acid, and 12*67 grs. of water. Of a 

 second portion, first boiled for a long time in water, and af- 

 terwards in successive portions of alcohol, as long as any- 

 thing seemed to be taken up, 8*74 grs. gave 26*447 of car- 

 bonic acid, and 9*86 of water. These are equivalent to 



1st. 2nd. 



Carbon 84*385 83*671 



Hydrogen 12*576 12-535 



96*961 96*206 



And indicate the presence of from three to four per cent, of 

 oxygen in the portion of the bitumen which remains after the 

 action of alcohol and aether. 



3. The soft elastic bitumen is said by long keeping to be- 

 come hard and brittle. It is certain that portions of this 

 brittle kind occasionally occur imbedded in the softer mass. 



Of a specimen of this brittle variety having a vitreous 

 lustre and conchoidal fracture, 



a. 6-263 grs. gave 19*47 carbonic acid, and 6*957 of water. 



b. 5*93 grs. gave 18*48 6*63 



