798 



ORGANIC ANALYSIS. 



lated and uncoagulated state. When coagulated, 

 the separation of fibrin and albumen cannot be 

 effected by any means with which we are ac- 

 quainted, and, indeed, the first authorities 

 differ when they attempt to decide which of 

 the two they have to deal with, if they occur 

 in the coagulated state. When uncoagulated, 

 their separation and quantitative determination 

 may be effected with considerable accuracy. 

 Pure fibrin, when moist, is white and some- 

 what elastic, is insoluble in water, alcohol, or 

 ether. It is readily taken up by strong acetic 

 acid, and from this solution it is precipitated 

 by ferrocyanide of potassium (prussiate of pot- 

 ash); fibrin also dissolves in solution of pot- 

 ash ; if, when thus dissolved, it be he.ited gently 

 and the liquid neutralized by an acid, awhile 

 flocculent precipitate occurs, which redissolves 

 in excess of acid, and the solution emits an 

 odour of sulphuretted hydrogen. Strong nitric 

 acid turns fibrin yellow, forming a yellow so- 

 lution with gradual evolution of gas ; in con- 

 centrated hydrochloric acid it slowly dissolves 

 with a rich violet colour. These are properties 

 it possesses in common witli albumen and ca- 

 sein ; but it is distinguished from them and 

 from all other animal matters by its sponta- 

 neous coagulation when removed from the living 

 body. This furnishes us with a certain test 

 of its presence when in the liquid form, and 

 enables us to separate it in good degree from 

 other bodies; within its pores, however, is ob- 

 stinately retained a quantity ot the fluid from 

 which it has just separated itself, together with 

 most of the globules and particles suspended 

 in the secretion. It becomes necessary, there- 

 fore, to wash out these ingredients, an opera- 

 tion rendered possible by the insolubility of the 

 fibrin in cold water. The coagulum from a 

 known quantity of fluid is cut into very thin 

 shreds by a sharp knife, tied in a piece of linen, 

 and a gentle stream of water allowed to fall 

 upon it; from time to time the clot is gently 

 kneaded and the washing continued; in the 

 case of blood, till all traces of colouring matter 

 are removed, or, where no colour is present, so 

 long as may be deemed necessary; the residue 

 is then removed from the linen, dried, digested 

 in ether to remove adhering fatty matters, again 

 dried and weighed. A portion is then incinerated, 

 the weight of the fixed matters determined and 

 deducted from the gross weight of the dried 

 fibrin, by which we obtain that of the organic 

 matter.* 



Fatty matters. Several peculiar oily sub- 

 stances occur in the fluids and solids of the 

 animal body. Among the saponifiable fats 

 chemists have distinctly ascertained the pre- 

 sence of margarin, elain, and butyrin ; besides 

 these we have cholesterin and serolin, which 

 are not saponifiable by boiling in alkaline solu- 

 tions, and there are others containing phos- 

 phorus and sulphur, but their composition and 

 properties are yet involved in uncertainty. Our 



* It has been objected that the insoluble nuclei 

 of the red particles are retained in this process. It 

 is, however, superior, both in the accuracy of its 

 results and the facility of its performance, to any 

 other method hitherto proposed as its substitute. 



analytical processes for separating these bodies 

 are very imperfect ; the fats are all soluble in 

 boiling alcohol, and still more freely in ether. 

 Cholesterin and serolin may be isolated from 

 the other fats by boiling the residue, after eva- 

 poniiion of theeiher, with solution of caustic 

 potash, as they remain undissolved by this 

 menstruum, whilst the mandarin, elain, and 

 butyrin form soaps which are dissolved by the 

 water. 



Senilin is an azoli.^ed fat, which has hitherto 

 only been found in the blood ; it is readily dis- 

 tinguished from cholesterin by its fusing point 

 being much lower, 97 F., whereas cholesterin 

 does not melt below 278, and is found in the 

 blood only in minute quantity. By pressing 

 them between folds of filtering paper we might 

 therefore, if careful to maintain a temperature 

 near that of boiling water, effect a tolerably 

 complete separation of these bodies. 



Butyrin rapidly absorbs oxygen from the 

 air, setting free a volatile acid, the butyric; 

 it possesses the peculiar odour of rancid butter, 

 by which its presence is always easily recog- 

 nized. 



In analytical inquiries it is best to separate 

 fatty matters by ether as the first step after the 

 liquid has been evaporated todryness; we may 

 then safely proceed to determine the 



Albumen. In chemical properties it differs 

 little from fibrin, excepting in the fact of its 

 requiring heat or some chemical agent to pro- 

 duce coagulation ; towards reagents it com- 

 ports itself in the same way. When liquid, 

 its separation from fibrin and fats is effected 

 as just described. The residue, after the 

 fats have been lemoved by ether, is di- 

 gested in boiling water, and the residue well 

 washed ; the albumen remains upon the filter, 

 and must be dried and weighed. A given 

 quantity is incinerated to determine the pro- 

 portion of saline matters, which must be de- 

 ducted from the weight previously found. If 

 uric acid existed in the solution, it would be 

 mixed with the albumen. In case the colour- 

 ing matter of the blood were contained in the 

 fluid, a small part would remain mixed with 

 the albumen, and might be removed by di- 

 gestion in alcohol acidulated with sulphuric 

 acid, by which the hsematosin is dissolved ; the 

 greater part, however, subsides by allowing 

 the liquid to stand undisturbed in a tall vessel 

 for forty-eight hours. If the solution contain 

 free alkali, a part of the albumen is redissolved 

 on the addition of water; when, therefore, the 

 filtered liquid presents an alkaline reaction, it 

 should be very carefully and exactly neutralized 

 by acetic acid, evaporated to dryness, and again 

 treated with hot water; the weight of this second 

 portion of albumen must be added to that first 

 obtained. Casein hardly ever occurs in the 

 same solution with albumen ; if present, it 

 would be separated by the acetic acid in the 

 manner already described. 



Casein is distinguished from albumen by its 

 non-coagulability by heat ; when its solutions 

 are evaporated at a high temperature, an inso- 

 luble skin or film forms upon the surface, 

 which is almost characteristic, the only thing 



