1 8 13.] Chemical Properties of Animal Fluids. 21 



reddens turnsol paper, but which without a fresh addition of 

 acetic acid is insoluble both in cold and boiling water. The 

 solution of fibrin in acetic acid added to prussiateof potash or of 

 ammonia, gives a white precipitate, without any separation of 

 prussic acid. This solution will also produce a precipitate by 

 alkalies, but it is redissolved by a small excess of the latter. 

 Sulphuric, nitric, and muriatic acids afford likewise a precipitate" 

 with this solution : and the precipitate is composed, as we shall 

 presently set?, of fibrin and the acid employed. If the precipi- 

 tate be laid on a filter and washed, a certain quantity of this acid 

 is carried off by the water, and the remaining substance is 

 soluble in pure water. The solution contains a neutral combi- 

 nation of fibrin with the mineral acid employed, which is 

 mucous, somewhat opaline, and of an acidulous taste. An 

 addition of acid will again precipitate it, and it thus often 

 happens that an animal substance, that has been treated with a 

 mineral acid and washed on the filter, gives at length a clear 

 liquor, which becomes turbid on falling into the acid liquor that 

 had first gone through. This phenomenon always indicates the 

 presence of the above-mentioned combination of" a mineral acid 

 with fibrin, or with albumen, which appears to possess the same 

 chemical properties as fibrin.* 



4. In weak muriatic acid fibrin shrinks and gives out a small 

 quantity of azotic gas; but scarcely any portion i 5 dissolved even 

 by boiling : neither does the acid liquor afford any precipitate 

 with ammonia, or with prussiate of potash. Evaporated to 

 dryness a brownish residue is obtained, from which potash dis- 

 engages a little ammonia. Concentrated muriatic acid decom- 

 poses fibrin by coction, and produces a red or violet coloured 

 solution. 



The fibrin that has been digested with weak muriatic acid is 

 hard and shrivelled. By washing repeatedly with water it is 

 at length converted into a gelatinous mass, which is perfectly 

 soluble in tepid water. The solution powerfully reddens litmus 

 paper, and yields a precipitate with acids as we if as with alkalies. 

 Fibrin has therefore the property of combining with muriatic 

 acid in two proportions. The one gives a neutral combination 

 soluble in water; the other a combination with excess of acid 

 which is insoluble, but which is reduced to the state of the 

 soluble compound by the action of pure water. 



^ 5. Concentrated sulphuric a, id decomposes and carbonises 

 fibrin. The same acid diluted with six times its weight of wrtjer 

 and digested with fibrin, acquires a red colour, but dissolves 

 scarcely any thing. The fibrin that is not dissolved is a combi- 

 nation of it with an excess of sulphuric acid. By depriving it 



• It m;iy Ik- ' i>-<rvc-«i thai ili,- precipitate produced by utrle acid nfoifiel a 

 jrHl.nv colour, but bat in oilier rejects the mine propcrtiesai toe (wo oilier.-.. 



