

198 EXAMINATION OF A NAPHTHA FROM LIME-SOAP. 



* 





Air remaining in balloon, 

 Height of barometer, 

 Density of vapor found, 



" " theoretical (C20 H20), 



Its sp. gr. was found to be 0.7912, at 



c. c. 



769.3mm. a t 050 



• 4.9166 

 4.841 



The fraction 1G5°-166° was treated at once with monohydrated sulphuric acid. The 

 first portion of acid blackened very much, and heat was evolved, but no very great amount 

 of viscid matter separated ; the second portion of acid also blackened very much, but 

 was unusually free from viscidity ; the third portion acted much less than the second, and 

 the fourth and fifth portions much less than the third, though considerable heat was 

 evolved throughout. The hydro-carbon at last became strongly colored, and much sul- 

 phurous acid was evolved. It was washed, dried, and boiled upon sodium in the usual 





way 



On combustion, 0.2294 grin, of the hydro-carbon gave 0.285 grm. water, and 0.7264 



grin, carbonic acid 



t 



Found. 



Carbon 86.36 



Hydrogen 13.77 



100.13 



These numbers give the empirical formula C 18 H 17 . 2 . 



Previous to the above-mentioned examination of the two extremities of this heap, 

 but not until long after the heap itself had been obtained, an attempt was made to 

 hasten operations by working upon it alone ; the ten or twelve most prominent frac- 

 tions of the heap having been selected and repeatedly redistilled, to the exclusion of all 

 other fractions, both above and below, in the hope that products of nearly constant 

 boiling point might thus be more quickly procured. At the commencement of this 

 special operation the common difference between each of the fractions was about one 

 degree, that is, at each successive distillation each of the fractions began to boil about 

 one degree lower than it did in the preceding distillation, and the distillatory process 

 was continued until this common difference had been reduced to one-third of one de- 

 gree ; the portions of distillate more volatile than the selected fraction of lowest boiling 

 point, and of residue less volatile than the selected fraction of highest boiling point, be- 

 ing meanwhile added to the'fractions in the old series, now excluded from the distilla- 

 tion, which had been taken off at similar temperatures. It may here be said that this 

 operation was not found to be advantageous, and we do not in any way commend it, 

 at least when applied, as above, to bodies which have already been brought to such a 

 condition that their boiling points are tolerably constant. 



