Chemical Examination of Burmese Naphtha, or Rangoon Tar. 513 



heated by passing, before it eutered the still, through a system of 

 pipes the temperature of which could be regulated. Treated in this 

 way, it furnishes 96 per cent, of volatile products, fluid and solid. 



Steam of 100° C. (212° F.) carries over 11 per cent, of a volatile 

 oil perfectly free from solid hydrocarbons, which at that tempera- 

 ture are entirely retained in the distillatory apparatus. Between the 

 temperatures of 110° and 145° C. (230°-29.S° F.), 10 per cent, of a 

 further distillate is obtained, which is almost free from solid hydro- 

 carbons. The temperature may be raised to 100° C. (320° F.) 

 without materially augmenting this per-centage ; but on gradually 

 increasing the temperature of the steam to the fusion-point of lead, 

 the operation yields 20 additional per cent, of distillate, which retains 

 its fluidity at 0° C. (32° F.), notwithstanding the presence in it of an 

 appreciable quantity of solid matter. At this stage of the process 

 the products of distillation begin to solidify on cooling, and about 

 31 per cent, of a crystalline material is obtained sufliciently consistent 

 to be submitted to pressure. After this the consistence of the pro- 

 ducts of distillation begins to cUminish ; and whilst the temperature 

 of the steam is considerably raised, 21 per cent, of a mixture of solids 

 and liquids distil, the latter predominating especially as the operation 

 proceeds. 



In the last stage of the process the distillate completely changes its 

 character, becoming very dark in colour, of a pitch-like consistence, 

 and exhibiting scarcely an indication of the presence of crystalline 

 matter. When this product, which amounts to about 3 per cent., 

 has passed over, there remains in the still a coke-like mass, which 

 contains a small quantity of earthy impurities. 



Although there is a considerable difference between the specific gra- 

 vities of the first and last fractions of the distillates, all the products 

 of distillation, like the original oil, are lighter than water, and could 

 be separated therefore by means of the well-known apparatus (called 

 a Florentine flask) employed in the distillation of essential oils. 



By exposing the distillates obtained beyond the temperature of 

 145° C. (293° F.) to a freezing mixture, nearly all the crystalline 

 matter solidified, and became removeable by means of filtration and 

 pressure. It was thus ascertained that Rangoon tar contains from 

 10 to 11 per cent, of solid constituents (paraffine). 



Solid Constituents. 



The solid product, when removed from the fluid hydrocarbons, 

 still retains a portion of the latter with much obstinacy ; in order to 

 purify the solid, it has to be subjected to the action of boiling con- 

 centrated sulphuric acid, and to be subsequently washed, first with 

 an alkaline solution, then with water. On redistillation, the paraffine is 

 obtained quite white, but even now it still retains some fluid hydro- 

 carbons which have resisted the action of the sulphuric acid ; the 

 greater part can be removed by pressure between folds of cloth in a 

 powerful hydraulic press and subsequent exposure for some months 

 to the air, in which the fluids gradually disperse. By fractional 

 crystallization from hot alcohol, we have been enabled to separate the 



