1818.] their Combinations with Alkalies. 193 



and lead. After giving a detail of the processes which he 

 employed with these substances respectively, he draws the 

 following general conclusions. Soda, barytes, strontian, lime, 

 the oxide of zinc, and the protoxide of lead, convert fat into 

 margarine, fluid fat, the sweet principle, the yellow colouring prin- 

 ciple, and the odorous principle, precisely in the same manner as 

 potash. Whatever be the base that has been employed, the 

 products of saponification always exist in the same relative 

 proportion. As the above-mentioned bases form with marga- 

 rine and the fluid fat compounds which are insoluble in water, it 

 follows that the action of this liquid, as a solvent of soap, is not 

 essential to the process of saponification. It is remarkable that 

 the oxides of zinc and of lead, which are insoluble in water, and 

 which produce compounds equally insoluble, should give the 

 same results with potash and soda, a circumstance which proves 

 that those oxides have a strong alkaline power. Although the 

 analogy of magnesia to the alkalies is, in other respects, so 

 striking, yet we find that it cannot convert fat into soap under 

 the same circumstances with the oxides of zinc and lead. But 

 although magnesia does not saponify fat, it forms with it an 

 homogenous substance, from which the fat does not separate 

 even when placed in boiling water, notwithstanding the differ- 

 ence in the specific gravity of the ingredients. Alumine that 

 has been mixed with fat is entirely separated from it by this 

 means. Hence we may establish three gradations in the action 

 of salifiable bases on fat, that in which a perfect saponification 

 is produced, as is the case with the alkalies, where there is a 

 union but not a proper saponification, as with magnesia, 

 and where there appears to be no union, as in the case of 

 alumine. 



The author next proceeds to examine the quantity of fat which 

 a given weight of potash can saponify, in order to form a stan- 

 dard of comparison for the other saponaceous compounds, when 

 it was found that 100 parts of hog's-lard were reduced to the 

 completely saponified state by 16-36 parts of potash. He now 

 enters upon the consideration of the different soaps that are 

 capable of being formed by the margarine and the fluid fat 

 respectively, and endeavours to estimate the proportions of which 

 they consist. The soap composed of margarine and potash, as 

 has been stated above, exists in two proportions, the saturated 

 compound, consisting of 100 parts of margarine to 17*77 of 

 potash ; the other, or the super-margarate, consisting of 100 

 parts of margarine to only half the former quantity of potash, 

 8 - 8 parts. It is observed that in the first of these combinations 

 the margarine saturates a quantity of base, which contains three 

 parts of oxygen, proceeding upon the estimate that 100 parts of 

 potash contain 17 of oxygen. M. Chevreul then prepared 

 soaps composed of margarine and soda, margarine and barytes, 

 margarine and strontian, and margarine and lime ; by decom- 

 posing them by an acid, aad finding the quantity of neutral or 

 • Vol. XII. N° III. N 



