of Heat and Pressure upon the Paraffins. 185 



of the hand is sufficient to liquefy it, and after about a dozen distillations 

 it remains permanently liquid. Although there is no difficulty in thus 

 ultimately effecting the resolution of the solid paraffin into liquid pro- 

 ducts, the rapidity of the transformation seems to be dependent upon 

 conditions which we cannot yet say we have satisfactorily determined. 

 On one occasion, after all the paraffin had been distilled over and had 

 solidified in the colder limb of the tube, the empty portion in contact 

 with the flame became softened and blew out, when instantly, on the 

 removal of the pressure, the solid matter became liquid, and slightly 

 effervesced as if gas had been condensed in the substance by the pressure 

 to which it had been subjected. It seems to be absolutely necessary 

 that the paraffin should be thus distilled over and condensed ; by merely 

 heating it in the tube in such a manner that the condensed vapours flow 

 back again upon the heated portion, the liquefaction of the paraffin is 

 never accomplished. About 6 grms. of a pure paraffin, melting at 

 41°*5 0. (see section 12), were heated in a sealed tube to about 200° for 

 twelve hours, but the melting-point remained unchanged. The same 

 portion of paraffin was then transferred to a \f-tube surrounded by 

 wire gauze, and distilled backwards and forwards in the combustion- 

 furnace. After six distillations it was rendered completely liquid. The 

 total quantity of liquid obtained was about 6 cub. centims. On gently 

 warming it, bubbles of gas were evolved, and the liquid was in full 

 ebullition at 40°, but only about one sixth came over below 100° ; about 

 2J cub. centims. distilled between 100° and 200°, and nearly the whole 

 of the remainder below 300°; the small quantity remaining solidified 

 when the bulb was plunged into cold water. 



2. It appears that only paraffins boiling at an extremely high tempe- 

 rature, and those usually solid under ordinary conditions, are thus sus- 

 ceptible of decomposition. The readiness with which they yield liquid 

 hydrocarbons appears to depend upon the complexity of their constitu- 

 tion. We have not determined with certainty the limits of the decom- 

 position; but we find that the paraffin (and olefine) boiling at about 255° 

 (see section 11) may be repeatedly distilled backwards and forwards in a 

 sealed ^-tube without suffering the slightest change. 6-7 grms. of the 

 mixture of hydrocarbons were distilled backwards and forwards twenty- 

 one times ; but on opening the tube no gas was evolved, and the boiling- 

 point (252°-255° uncorrected) remained unaltered. A further proof of 

 its unalterability on repeated distillation under pressure is afforded by its 

 reaction with bromine (see section 5). 



I. 9*38 grms. of the mixed hydrocarbons before distillation required 

 2*95 grms. of bromine before the liquid became permanently reddened ; 

 100 parts by weight would require 31*4. 



II. 8-605 grms. hydrocarbon before distillation required 2-672 grms. of 

 bromine, or 100 grms. would require 31 of bromine. Mean amount of 

 bromine needed 31-2 per cent. 



