fnagnefia. 



272 XXPSR1MENTS ON ASTRINGENT VEGETABLES. 



cfenfe light fawn coloured precipitates. With ftrong nitrous 

 acid they effervefced ; and loft their power of precipitating th<j 

 folutions of ifinglafs, and the falts of iron. The pure alkalis 

 entered into union with their tannin, fo as to prevent it from 

 being acted upon by gelatine. 

 — with the fo- When the folutions of lime, of ftrontia, or of barytes, were 

 fuble earths. poured into the infufions, copious precipitates, of a thade of light 

 brown, were formed ; and the refidual fluid aflumed a paler 

 tint of red, and was found to have loft its power of precipi- 

 tating gelatine, 

 time, magnefia, After lime had been boiled for fome time with a portion of 

 carbonate of the infufion, it aflumed a dull red colour. The liquor that 

 paITed from it through the riltre had only a faint tint of red, 

 did not act upon gelatine, and feemed to contain only a very 

 fmall portion of vegetable matter. Pure magnefia, when heated 

 with the infufion, acted upon it in an analogous manner ; the 

 magnefia became light red, and the refidual fluid had only a 

 very flight tinge of that colour. With carbonate of magnefia, 

 the infufion became deeper in colour, and loft its power of 

 precipitating gelatine; though it ftill gave, with oxygenated 

 fulphate of iron, a light olive precipitate. 

 Carbonates of The carbonates of potafli, of foda, and of ammonia, in their 



potato, foda, concentrated folutions, produced onlv a flight degree of turbid- 

 ammoma. _ - • t , ^ ' J ., 



nets in the infufion of catechu ; they communicated to them a 



darker colour, and deprived them of the power of acting upon 

 gelatine ; though this power was reftored by the addition of 

 an acid. 

 Expofare to the After the mixture of the folution of carbonate of potafli and 

 * r * the infufions had been expofed to the atmofphere for fome 



hours, a brown crufl was found to have formed upon its furface, 

 and a flight precipitation had taken place 

 Aluminous falts The falts of alumine precipitated the infufions, but lefs co- 

 catechu. 10 " ° P' ou fly than they precipitate the infufion of galls. A fimilar 

 effect was produced by nitrate of potafli, fulphate of magnefia, 

 prufliate of potafli, and many other neutral falts. 

 Kitrate or ace- The nitrate, or acetite, of lead, in concentrated folution, 

 ticeof lead. when poured into the infufion, produced in it a denfe light 

 brown precipitate, which gave to the fluid a gelatinous appear- 

 ance. After this effect, there was no free acid found in it; 

 and both the tannin and the extractive matter feemed to have 

 been carried down, in union with a portion of the metallic fait. 



The 



