COAL-TAR AInTD WATER-GAS TAR CREOSOTES. 



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be carried out with the use of air under a pressure of 7 inches of 

 water until all the moisture had been expelled from the tar. The 

 rest of the distillation was completed without the use of air. The data 

 thus obtained represent creosote oils that any manufacturer could 

 obtain from the same tar. If 

 there is any difference, the oils 

 are lower in index of refrac- 

 tion and specific gravity, and 

 higher in sulphonation residue 

 than they would have been 

 with the use of air. In other 

 words, any specification that 

 might result from this investi- 

 gation would be on the safe 

 side and would work no hard- 

 ship on the manufacturer of 

 creosote oil. 



It was a somewhat difficult 

 matter to cut the distillates 

 from the tar in such a manner 

 that an oil could be obtained 

 having a distillation range 

 similar to that of a commer- 

 cial creosote. In practice, 

 therefore, no attempt was 

 made to separate the light 

 oils from the creosote oils in 

 the distillation from the tar 

 still. The only separation 

 made was the fraction con- 

 taining the water an'd the 

 more volatile of the light oils. 

 The total distillate above this 

 point was collected in one con- 

 tainer and subsequently dis- 

 tilled from an ordinary flask. 

 All oil coming over below 205° 

 C. was discarded. That boil- 

 ing from 205° to 235° C. was 

 collected separately. The 

 residue above 235° C. was 

 weighed, and to this was added 25 per cent of its weight of the frac- 

 tion boiling between 205° and 235° C. In this way the creosotes were 

 made to conform to specification No. 1 of the American Railway Engi- 

 neering Association so far as distillation limits were concerned. 



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139 



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2-^0 260 aeo 300 



TEMPERATURE (NOT CORRECT E DJ^C 

 Fig. 17.— Index of refraction values of coal-tar creosotes pro- 

 duced from tars No. 3 and No. 4. 



Commercial coal-tar creosotes — Dotted lines. 

 Experimental coal-tar creosotes — Solid lines. 















































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