MABERY. — SULPHUR PETROLEUMS. 9 



shown by the rapid coloration of the oils when distilled, even after 

 removal of the sulphides by mercuric chloride. Nevertheless, in the 

 separation of coi^stituents requiring larger quantities of distillates than 

 can conveniently be collected in vacuo, since only porcelain or earthen 

 ware stills are admissible on account of the decomposition in metallic 

 stills, it may be necessary to depend to a limited extent upon refinery 

 distillates. 



After the first distillation of the crude oils in vacuo, distillation of 

 the portion collected below 150° was continued under atmospheric 

 pressure, since it occasioned no appreciable decomposition. Under the 

 diminished pressure some loss of the constituents with low boiling 

 points could not be avoided ; but this was not important, since refinery 

 distillates could be utilized for the separation of the volatile hydrocar- 

 bons. Distillation of considerable quantities of oil in vacuo presented 

 certain difficulties. Neither glass nor metallic stills were suitable, and 

 no American earthen ware stills could be procured that would support 

 a vacuum on account of porosity from imperfect moulding and glazing. 

 Some of the English earthen ware has supported a vacuum, but the 

 ideal stills for such work, or for any distillations in large quantities, 

 when metals cannot be employed, are those manufactured in the 

 Royal Berlin Porcelain Factory. We have had a three-gallon porce- 

 lain still and several others of smaller capacity in operation almost 

 continuously during several months with apparently no deterioration. 

 When these stills are enclosed within a brick chamber, the tempera- 

 ture of distillation may, without difficulty, be carried above 350° by 

 means of large laboratory burners. Another serious obstacle imme- 

 diately presented itself in the porosity of common corks, which alone 

 could be used for connections. After much labor it was found that 

 tight joints could be secured by means of a rubber lute made by dis- 

 solving gum rubber in very light gasoline. Thin films of this lute 

 drawn by the inward pressure into the joints and imperfections in the 

 corks, after several applications, formed sufficiently close connections. 

 Any other than the lightest gasoline as a solvent leaves a sticky film 

 that is unpleasant to manipulate. 



An important feature in prolonged fractional distillations in vacuo is 

 a simple and convenient means for maintaining, without too close 

 attention, a constant tension within the still. Air must not come in 

 contact with the hot oil or vapor, and it would require too large quan- 

 tities of an inert gas. An expedient suggested itself in the fact that 

 occasionally small leaks held the manometer column stationary at what- 

 ever height it happened to stand. It therefore seemed possible to 



