A solution of recently-fused phosphoric acid acts upon fibrine in the same way as the sul phuric acid ; but if the acid solution has been kept for some weeks, the fibrine then forms with it a soluble jelly, which is not precipitated by excess of acid.
Concentrated acetic acid converts fibrine into a jelly easily soluble in warm water. When this solution is boiled,a little nitrogen is evolved, but nothing is precipitated ; when gently eva porated, it gelatinises, and leaves, on desic cation, an opaque insoluble residue. The other acids added to this acetic solution produce precipitates which are compounds of fibrine with the added acid. Fibrine is also preci pitated from the acetic solution by caustic pot assa, but is redissolved by excess of alkali.
The acetic solution of fibrine is precipitated in white flakes by ferrocyanuret of potassium : this precipitate, when dried, appears to be a compound of fibrine with cyanuret of iron and hydrocyanic acid ; it is insoluble in dilute acids, but is decomposed by caustic alkalis, which abstract the cyanuret of iron and hydro cyanic acid, and the remaining fibrine first gelatinises and then dissolves. 100 parts of this compound, carefully dried at and then incinerated in a weighed platinum cru cible, gave 2.8 red oxide of iron,=7.8 of the combination of cyanuret of iron with hydro cyanic acid ; whence it follows that 92.2 of fibrine were contained in the white precipitated compound.
Caustic potassa, even much diluted, dissolves fibrine. if the solution is very dilute, the fibrine gradually forms a bulky jelly, which, heated in a close vessel to about 1300, dissolves into a pale yellow liquid, not quite transparent, and which soon clogs a filter. The yellow tint appears to arise from the presence of a small portion of adhering hzematosin. When this alkaline solution is saturated by muriatic or acetic acid, it exhales a peculiar fetid odour and blackens silver, announcing the presence of sulphur, so that the animal matter seems to have suffered some slight change. It is stated by Berzelius that fibrine is capable of neutral izing the alkali, and that such neutral com pound may be obtained by dissolving the fibrine in the alkaline solution, and adding acetic acid till it begins to occasion a precipi tate ; the filtered liquid is then perfectly neu tral, but thepotassa hears a very small propor tion to the fibrine. This neutral solution, he
says, much resembles white of egg, and is coagulated by alcohol and acids, though not by heat. Gently evaporated, it gelatinises, and, when dry, assumes the appearance of albumen dried without coagulation. In this state it dissolves in warm water, and is first thrown down, and then redissolved by the acids when added in excess. Alcohol throws down nearly the whole of the fibrine from its neutral alkaline solution : if there be excess of alkali, much of the fibrine is retained. Air. Ilatchett found that fibrine, when digested in strong caustic potassa, evolved ammonia and yielded a species of soap; acids occasion a precipitate in this solution which is altered fibrine, for it neither gelati irises nor dissolves in acetic acid: ammonia acts aspotassa, but less energetically.
When fibrine is digested in solution of per sulphate of iron, or of copper, or of perchlo ride of mercury, it combines with those salts, shrinks up, and loses all tendency to putre faction. When the alkaline solution of fibrine is decomposed by metallic salts, the precipitate consists of the fibrine in combination with the metallic oxide; some of these compounds are soluble in caustic potassa.
Tannin combines with fibrine, and occasions a precipitate both in its alkaline and acid solu tions: the tanned fibrine resists putrefaction.
The ultimate composition of fibrine has been determined by Gay Lussac and Thenard, and by Michaelis, who made a comparative ana lysis of that of arterial and venous blood : the following are their results:— Gay Lussac Michaelis.
and Thcnard. Arterial. Venous.
Nitrogen ..19.934 17.587 17.267 Carbon ..53.360 51.374 50.440 Hydrogen 7.021 7.254 8.228 Oxygen ..19.685 23.785 24.065 100.000 100.000 100.000The mean of these results gives nearly the fol lowing atomic composition: — Atoms. Equivalents. Theory.