Selenium in Commercial Suliilmric Acid. 315 



805 specific gravity. It may be as well to mention here, in 

 order to avoid repetition, that the heavy fractions at the end 

 of light oil distillations are mixed with the light fractions at 

 the beginning of the distillation of the heavy portion, and 

 thus carried on to the finished state. Thus, the decimal 84 

 to 85 oil is mixed with the decimal 84 to 85 oil from the 

 beginning of the distillation of the heavy portion, and they 

 are both washed together, and then form what is known 

 under the various names of marine oil (from its application 

 to ships' lamps), mineral colza, or under the commonplace 

 title 840/50 oil. It is somewhat a waste product, perhaps 

 its principal use at present being 840/50 Bloomless for the 

 adulteration of rape and other high-priced vegetable oils. 

 If the decimal 805 fraction is wanted as " crystal oil;' it is 

 treated with acid and a weak solution of soda, and after a 

 washing with water it is ready for the market. 



If it is wanted as No. 1 burning oil, it is washed with 

 acid and a strong solution of soda, again distilled, and with- 

 out treatment it is ready for the market. This process may 

 seem curious, but the idea is to get as good a light from the 

 No. 1 burning oil as from crystal oil, without the same 

 crusting of the wick occurring, as in crystal oil, due to the 

 presence of minute traces of sodium sulpho-olefines. 



The heavy portion, containing the solid paraffines, is taken 

 in a liquid state to the parafiine sheds, where paraffine of a 

 melting point about 118° Fahrenheit is taken from it by 

 means of a freezing machine, filter presses, and hydraulic 

 presses. This crude or green scale contains about 4 per 

 cent, oil and 2 per cent, dirt and water, and is the sub- 

 stance most largely used in the manufacture of parafiine 

 candles. 



The oil pressed from this green scale is known as blue oil 

 and after the separation it is taken and treated with acid and 

 soda as I have previously described. From the washer it is 

 pumped into what are known as the kibricating or ''luh" 

 stills, and is there fractionated practically into decimal 865 

 and decimal 885 oils. I may mention that, in order to bleach 

 the oil, it is treated with solid caustic soda in the stills — that 

 is, solid caustic soda is hung in the still in order that it may 



