18 SUBSTANCES SOLUBLE IN PETROLEUM SPIRIT. 



56 - 6, and subsequently one melting at 62, the conclusion to be 

 drawn is that the last is palmitic acid, and that the fractions with 

 lower melting-points consist of mixtures of stearic and palmitic 

 acids. According to Heintz's table a mixture of equal parts of 

 stearic and palmitic acid should melt at 56*6, and assume on 

 cooling a lamellar crystalline structure. Should no palmitic acid 

 have been found, but in its stead a fat-acid melting at about 53 

 to 54, the presence of myristic acid is to be inferred and the 

 mixture melting at 56 '6 would contain about 55 parts of stearic 

 to 45 of myristic acid. 



It is easy therefore to understand that if these observations be 

 correctly interpreted a rough judgment may be formed of the 

 amount of the separate acids present in the fat. 



At the ordinary temperature pure stearic add dissolves in about 

 40 parts of absolute alcohol, but in much less ether. When 

 suspended in water it may easily be collected and removed by 

 agitation with the latter solvent. The barium and calcium salts 

 are soluble in boiling alcohol, but the major part separates out 

 again on cooling. 



Palmitic acid dissolves much more easily in warm and cold 

 alcohol, and is very soluble in ether. It may also be collected 

 when suspended in water by shaking with ether. 



19. Okie Acid, etc. The alcoholic liquid from 16, which 

 gives no further precipitate on the addition of acetate of magne- 

 sium and ammonia, may be freed from alcohol by distillation 

 under diminished pressure. That may be accomplished, both in 

 this and many other cases, in the following manner: A retort 

 is charged with the liquid, into which a few pieces of scrap 

 platinum may with advantage be introduced, and attached to a 

 Liebig's condenser provided with a tubulated receiver, care being 

 taken that all connections are air-tight. The exhausting tube of 

 a Bunsen's air-pump is then introduced into the tubulure of the 

 receiver. Even if the evacuation be carried to only one-half an 

 atmosphere, aqueous infusions, etc., may be rapidly concentrated on 

 the water-bath and decomposition thus avoided which would other- 

 wise easily be caused by overheating, or by the action of the air, etc. 



After the recovery of the alcohol by distillation, the residue is 

 poured from the retort, which may be rinsed with a little water, 

 and acidulated with hydrochloric acid. The fat-acid which col- 

 lects on the surface of the liquid may be removed mechanically, 





