202 Chemical Inquiries into the Nature of several 



only one of the elements of the combitiation, attracts a portion ■• 

 of the latter with more force than the insoluble element does. 



33. Margarine decomposes the siibcarbonate of potash. We 

 may render the decomposition evident, by passing into a tube 

 fall of mercury a mixture of eight parts of water, one of mar- 

 garine, and half a part of subcarbonate, and by heating it after- 

 wards with a red-hot iron to ebullition. After cooUng we find 

 a gaseous residue which is pure carbonic acid. By repeating 

 the experiment in a small phial furnished with a curved tube, I 

 observed that the margarine was dissolved before there was any 

 extrication of carbonic gas, and that this extrication only took 

 place when the liquor boiled. This circumstance induced me 

 to think that, at the temperature at which margarine may be 

 united with potarjh, the carbonic acid which is separated from it 

 mav act upon a portion of subcarbonate, and convert it Into sa- 

 turated carbonate, and that it is afterwards the latter which 

 sends out carbonic acid at the temperature of boiling water. 

 The combination of margarine formed in this operation gave 

 me, after having been washed, margarine 100, potash S-S8 ; it 

 was therefore pearly matter. The liquor from which it was se- 

 parated, filtered several times, presented only some particles of 

 margarine, although it contained a great excess of alkaline car- 

 bonate. 



Action of Margarine %ipon Turnsole. 



34. The strong affinity of margarine for potash having' made 

 me think that this substance could redden turnsole, I put three 

 grammes into the aqueous extract of turnsole : when cold there 

 was no action; but when heatedthe margarine became soft, with- 

 out melting however, and the blue colour became red. I de- 

 canted the cooled liquor, and boiled several times the solid 

 matter which was separated from it with new extract of turn- 

 sole. 1 filtered, and there remained upon the paper red clots 

 and a blue semi-gelatinous matter, which became partly red 

 when dried : each of these suljstances was dissolved by boiling 

 alcohol : the two solutions were red, and deposited upon cooling 

 small crystals : those coming from the former yielded margarine 

 100, potash 7*5; those of the latter, margarine 100, and potash 

 8*45. As I made these determinations on very small quantities 

 only, I cannot vouch for their perfect accuracy ; they are suffi- 

 cient at least to establish that margarine takes up the potash 

 from the colouring principle of turnsole, and that it acts like 

 the acids. 



35. The affinity of margarine for potash is not only sufficiently 

 large to determine the formation of the pearly matter at the 

 expense of the alkali of the turnsole dissolved in water, but it la 



I also 



