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Mr. W. J. Wonfor on the Acids 



[Mar. 31, 



II. "On the Acids contained in Crab-oil." By William J. Wonfob, 

 Student in the Laboratory of the Government School of Science, 

 Dublin. Communicated by Dr. Maxwell Simpson. Received 

 March 7, 1870. 



Crab-oil is obtained from the nuts of a tree named by botanists Hylo- 

 carpus carapa, and also Carapa Guianensis. The tree grows abundantly 

 in the forests of British Guiana ; the oil is prepared by the Indians, who 

 bring it to George Town for sale. The oil is obtained from the kernels by 

 boiling them for some time, and then placing them in heaps and leaving 

 them for some days ; they are then skinned, and afterwards triturated in 

 wooden mortars until reduced to a paste, which is spread on inclined boards 

 and exposed to the sun ; the oil is thus melted out, and trickles into 

 receiving-vessels. 



As no investigation, so far as I have been able to ascertain, has ever been 

 made of the acids contained in this oil, Professor Galloway, to whom I am 

 indebted for the samples of the oil, recommended me to examine them ; and 

 the examination was conducted under his direction. 



The oil was in the state in which it is sold by the Indians ; it possessed 

 the appearance of a semifluid butyraceous mass, evolving a peculiar pene- 

 trating odour ; its melting-point was 55° C. To obtain the acids, the oil was 

 saponified with a solution of potassic hydrate, and the soap thus obtained 

 dissolved in a large quantity of distilled water ; to the solution sodic chlo- 

 ride was added in considerable excess ; the soap which separated was 

 washed and afterwards dissolved, and the solution treated with hydro- 

 chloric acid ; the liberated fatty acids were collected and pressed, then 

 melted in boiling water, and frequently washed to remove all traces of sodic 

 chloride ; the acids were again saponified, and again treated with sodic 

 chloride, but the soda-soap was on this occasion decomposed with tartaric 

 acid. The mixed acids had a melting-point of 40° C. 



The acids were dissolved in boiling alcohol of 89 per cent. ; the solution, 

 on cooling, deposited a white radiated crystalline mass, which was repeatedly 

 recrystallized from alcohol until it acquired a constant melting-point ; it was 

 then saponified with a solution of potassic carbonate, and the solution of the 

 mixed potash salts was evaporated to dryness on the water-bath ; the fat 

 salt was then dissolved in absolute alcohol. The alcoholic solution, unless 

 extremely dilute, does not crystallize on cooling, but merely forms a strong 

 jelly, which was, after pressing, dissolved in water, and the fat acid sepa- 

 rated by a strong solution of tartaric acid ; the separated acid was washed 

 with boiling water until all potassic tartrate and tartaric acid were removed : 

 it was subsequently twice crystallized from absolute alcohol: its melting- 

 point was then found to be 57° C. The acid, when pure, presents the ap- 

 pearance of a white glistening radiated crystalline mass : two combustions 

 were made ; the acid employed in the two analyses was obtained from 

 two different saponifications : — 



