OLEIC ACID. 



repeatedly crystallised in moderately concentrated boiling alcohol, 

 till it form a dazzling white flocculent powder, which must be 

 decomposed with tartaric acid and thoroughly washed with water. 

 Pure oleic acid may be more rapidly obtained by causing it to solidify 

 by exposing it to a temperature of 6 or 7, and then submitting it to 

 strong pressure; as the above-mentioned products of oxidation 

 of oleic acid remain fluid, they become absorbed in the filtering 

 paper, and leave the oleic acid in a state of purity. Further, the 

 water must only be removed while the oleic acid is exposed to a 

 stream of carbonic acid, and all operations upon it should be con- 

 ducted at a temperature below + 10, since it very rapidly becomes 

 decomposed. 



Tests. If it be required to test a fat or a mixture of fatty acids 

 accurately for oleic acid, we must first isolate this acid by one of 

 the methods which we have described, and obtain it in a state of 

 at least tolerable purity, so as to enable us to ascertain the solubility 

 of the lead-salt in hot ether. Moreover, oleic acid possesses the 

 distinctive character of being the only one either of the oily or 

 solid fatty acids which, on dry distillation, yields sebacic acid an 

 acid which may be distinguished from the simultaneously formed 

 capric and caprylic acids by its crystallisability, and which we may 

 easily separate from them and recognise, by forming and crystal- 

 lising its baryta-salt. 



Physiological Relations. 



Occurrence. Oleic acid, in combination with alkalies, exists in 

 the blood and in the bile, and, in lesser quantity, in most of the 

 other animal fluids, except the urine : in combination with oxide 

 of lipyl, as a haloid salt, it occurs in the fat of the cellular tissue, 

 and, indeed, wherever free fat is found in the animal body. 



Uses. As the vegetable fats are, for the most part, far richer 

 in oleate of oxide of lipyl (olein) than animal fats, there seems to 

 be a reason for the assumption that one of the uses of oleic acid in 

 the animal body, is to form the more solid fats, margaric and stearic 

 acids ; a view which is supported by the nature of the action of 

 atmospheric air on oleic acid, (to which we have already referred,) 

 and by its conversion into an acid having the radical of margaric 

 acid. It might, however, have been expected d priori that animal fat 

 would contain more margarate than oleate of oxide of lipyl, since 

 oleic acid or an oleate is more rapidly consumed than margaric acid. 

 We must, however, here, as in many other departments of phy- 

 siological chemistry, rather abstain wholly from all conjectures 



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