Elaine from Oils.— Soap. 189 



S2. Compressibility of Water. — This experiment has been 

 tried bj the distinguished Danish philosopher (Ersted, by 

 an ingenious apparatus of his own invention. The result 

 is thus stated. " Agreeably to the mean of a great number 

 of experiments, a pressure equal to that of the atmosphere 

 produces in water, a diminution of volume of 0.000045. 

 In all the trials with my apparatus, from the pressure of i 

 to that of G atmospheres, I have the compression of water- 

 to be in the ratio of the compressing force. Canton had 

 obtained, in the greater number of his experiments, 0,000044 

 for a pressure equal to that of the atmosphere, which differs 

 only by one millionth from my result. The ingenious ex- 

 periments of Mr. Perkins, made with several hundred 

 atmospheres, give 0.0CG048 for each atmosphere. I am 

 induced to attribute this difference, in itself very small, to a 

 compression which the sides of his vessel (being of metal) 

 may have sustained. Another circumstance ought perhaps 

 also to be taken into consideration, viz. that water seems 

 to lose a little of its compressibility after several compres- 

 sions. I dare not, however, aver this to be the fact, not 

 having subjected it to a rigorous trial. — Idem. 



23. JVew process for oh^aining Elaine from Oils^ by M. 

 Peclet. — This process is founded on the property which 

 stearine possesses of becoming saponaceous in the cold by 

 strong lyes, which property does not belong to elaine. To 

 separate these two substances, pour upon oil a concentrated 

 solution of caustic soda, stir the mixture, heat it slightly to 

 separate the elaine from the soap of the stearine, pour it 

 on a cloth, and then separate by decantation the elaine 

 from the excess of alcaline solution. I have always suc- 

 ceeded in this process with all the oils, except with those 

 that are rancid or have become changed by heat. The 

 elaine obtained by this process is perfectly identical with 

 that procured by the processes of Chevreul and Bracon- 

 not. — An. de Chimie, Mars 1023. 



24. Soap. — M. Chevreul, in a memoir on the causes of the 

 difference which is observable in soap, with respect to its 

 degrees of hardness and softness, and its odour, arrives at 

 the following conclusions : 



