88 Dr. Apjohn on the Potatoe Spirit Oil 



Assuming this formula as the true one, the deficiency in 

 the carbon experimentally determined is not greater than 

 what usually takes place ; but the error in the hydrogen, 

 though trifling in amount, being upon the opposite side to 

 that on which it usually occurs, it became expedient to resort 

 to some method of verification. The specific gravity of the 

 vapour of the oil was therefore taken according to the well- 

 known method of Dumas. 



The weight of glass ball filled with dry air, the pressure 

 being 30*324 and temperature 48°*5, was 914*86 grs. 



The ball was sealed at 364<°, and then weighed 917*78 grs. 

 Hence 917*78 — 914*86 = 2'92 grains is the excess of the 

 weight of vapour in ball over that of the air displaced. 



The capillary end of the beak attached to the ball having 

 been broken under mercury, it was ascertained by the amount 

 of this metal which flowed into the ball, that its capacity 

 was 16*76 cubic inches, which, at a pressure = 30, and a 

 temperature = 60°, will (supposing it air) become 16*76 



448 + 60 30*324 %Ho6m u - . i « ,,, 



X A — — tttt X — — — = 17*333 cubic inches. Jbrom this 

 448+48*5 30 



must be subtracted *1 cubic inch which was found to remain 

 in the balloon, so that the bulk of air excluded by the vapour, 

 when reduced to the mean temperature and pressure, was 

 17*233 cubic inches, whose weight = 5'344 grains. Hence 

 2*92 + 5*344 = 10*264 is in grains the weight of the va- 

 pour. 



The capacity of the glass balloon at 48°* 5 being 16*76 cubic 

 inches, it will, owing to the expansion of glass, become at 364° 

 16*843 inches. This therefore is the volume of the vapour 

 and bubble of air at 364°. But the volume of the latter be- 

 ing 0*1, it will at 364° become 0*16. Hence the true volume 

 of the vapour at 364° = 16-84S — 0*16 = 16*683 ; so that 



16*683 x tto + !? X 3 °2 24! = 10'549 is the volume of the 

 448 + 364 30 



vapour reduced to a temperature = 60° and pressure = 30. 



But as this weighs 10*264 grains, 100 cubic inches of it would 



weigh 97*298 grains. The specific gravity therefore of the 



. 97*298 ft . 



va *w is sTom^ 3137 ' 



Now if the composition of the oil be C 5 H 6 O^ the specific 

 gravity got by adding together the products of the densities 

 of the vapours of the different elements by the number of 

 atoms of each would be 3*072. But we have here so close a 

 correspondence between experiment and calculation, that no 

 doubt can remain as to the correctness of the basis on which 



