284 Dr. Thomson and Mr. Wood on the Composition of Shea Butter. 



for the improvement of Africa are so well known. The colour of the oil 

 is white, with a shade of green. It is solid at the usual temperature in 

 this country. At 95° it assumes the consistence of soft butter, and at 

 110° is a clear and liquid oil. "When boiled in alcohol, the greater part 

 is dissolved, and crystallizes on cooling, in needles. It dissolves in cold 

 ether, and separates in needles by evaporation. The oil was saponified 

 by means of caustic potash in a silver basin, the soap separated from its 

 solution by common salt, and decomposed by tartaric acid. After being 

 crystallized out from alcohol five or six times, and freed by pressure from 

 adhering oleic acid, the acid was obtained in fine pearly scales, fusing 

 at 142°. It was united with soda, and yielded a salt in fine pearly scales. 

 Its atomic weight was estimated by means of the silver salt. In the 

 first, second, and third experiments, the silver salt was formed by precipi- 

 tating an aqueous solution of nitrate of silver, by an aqueous solution of 

 the fatty acid united to soda. In the fourth and fifth experiments, an 

 alcoholic solution of the acid was precipitated by a solution of nitrate of 

 silver in alcohol, and hence the excess of acid. 



I. 3*73 grains of silver salt gave 1*05 metallic silver = 1*126 oxide of 

 silver ss 301 9 per cent. AgO. 



II. 10*65 grains of silver salt gave 3*01 silver = 3*221 oxide of silver 

 = 30*23 per cent. AgO. 



III. 2*85 grains gave *861 AgO = 3021 per cent. 



IV. 4-71 grains gave 1*30 silver = 1*394 AgO = 2953 per cent. 

 V. 2*72 grains gave *743 silver = *797 AgO = 29*30 per cent. 



The following table will express the per centage composition of the 

 silver salt by these five experiments : — 



I. II. III. IV. V. 



Acid, 69*81 ... 69*77 ... 69*79 ... 70*41 ... 70*70 



Oxide of silver,... 30*19 ... 30*23 ... 30*21 ... 29*59 . . 29*30 



Taking the mean of all these experiments, the constitution of the 

 silver salt will be — 



Acid, 70*10 



Oxide of silver, 29*90 



And the atomic weight of the anhydrous salt is — 



Acid, 33*97 



Oxide of silver, 14*50 



Or leaving out the two last determinations, we shall have as a mean for 

 the three higher results, the atomic weight of the acid equal to 33*82. 



To determine the composition of the anhydrous acid, the three following 

 analyses were made by means of oxide of copper, and chlorate of potash : — 



I. 285 grs. of silver salt gave HO = 2*30 grs. and C0 2 = 5*73 grs. 

 II. 3*91 i « > sa 3-39 ■ i = 7*87 - 



III. 3*667 « „ „ = 3*058 . . _ 7*334 ■ 



