BLO 



BLU 



1>;rmen. Hence its coagulation by heat, 

 and the other phenomena which albumen 

 usually exhibits. If serum be diluted with 

 six times its weight of water, and then 

 boiled to coagulate the albumen, the li- 

 quid which remains after the separation 

 of the coagulum, if it be gently evaporat- 

 ed till it becomes concentrated, and then 

 be allowed to cool, assumes the form of a 

 jelly. Consequently it contains gelatine. 

 If the coag-ulated serum be heated in a 

 silver vessel, the surface of the silver be- 

 comes black, being' converted into a sul- 

 phuret. Hence it is evident that it con- 

 tains sulphur : and Proust has ascertain- 

 ed that it is combined with ammonia in 

 the state of a hydrosulphuret. If serum 

 be mixed with twice its weight of water, 

 and, nfter coagulation by heat, the albu- 

 incn be separated by filtration, and the 

 liquid be slowly evaporated till it is con- 

 siderably concentrated, a number of crys- 

 tals are deposited when the liquid is left 

 standing in a cool place. These crystals 

 consist of carbonate of soda, muriate of 

 soda, besides phosphate of soda and phos- 

 phate of lime. The soda exists in the 

 blood in a caustic state, and seems to be 

 combined with the gelatine and albumen. 

 The carbonic acid combines with it dur- 

 ing evaporation. Thus it appears that 

 the serum of the blood contains albumen, 

 gelatine, hydrosulphuret of ammonia, so- 

 da, muriate of soda, phosphate of soda, 

 and phosphate of lime. These compo- 

 nent parts account for the coagulation oc- 

 casioned in the serum by acids and alco- 

 hol, and the precipitation produced by 

 tannin, acetate of lead, and other metallic 

 salts. The cruor, or clot, as it is some- 

 times called, is of a red colour, and pos- 

 'sesses considerable consistence. Its mean 

 specific gravity is about 1.245, If this 

 cruor be washed carefully by letting a 

 small jet of water fall upon it, till the 

 water runs oft' colourless, it is partly dis- 

 solved, and partly remains upon the 

 scarce. Thus it is separated into two por- 

 tions : namely, 1. A white, solid, elastic 

 substance, which has all the properties of 

 fibrin; 2. The portion held in solution by 

 the water, which consists of the colouring 

 matter, not, however, in a state of purity, 

 for it is impossible to separate the cruor 

 completely from the serum. We are in- 

 debted to Bueqtietfor the first precise set 

 of experiments on this last watery solu- 

 tion. It is of a, red colour. Bucquct 

 proved that it contained albumen and 

 Iron. Mengiiini had ascertained, that if 

 blood be evaporated todrynessby a gen- 

 ^Je heat, a quantity of iron may be sepa- 



rated from it by the magnet. The quan- 

 tity which he obtained was considerable; 

 according to him the blood of a healthy 

 man contains about two ounces of it 

 Now, as neither the scrum nor the fibrin 

 extracted from the cruor contains iron, it 

 follows of course, that the water holding 

 the colouring matter in solution must 

 contain the whole of that metal. This 

 watery solution gives a green colour to 

 syrup of violets. When exposed to tbe 

 air, it gradually deposits flakes, which, 

 have the properties of albumen. When 

 heated, a brown coloured scum gathers 

 on its surface. If it be evaporated to dry- 

 ness, and then mixed with alcohol, a por- 

 tion is dissolved, and the alcoholic solution 

 yields, by evaporation, a residuum, which 

 lathers like soap in water, and tinges ve- 

 getable blues green : the acids occasion 

 a precipitate from its solution. This sub- 

 stance is a compound of albumen and so- 

 da. Thus we see that the watery solu- 

 tion contains albumen, iron, and soda. 

 When new-drawn blood is stirred briskly 

 round with a stick, or the hand, the whole 

 of the fibrin collects together upon the 

 stick, and in this manner may be sepa- 

 rated altogether from the rest of the 

 blood. The red globules, in this case, 

 remain behind in the serum. It is in this 

 manner that the blood is prepared for the 

 different purposes to which it is put ; as 

 clarifying sugar, making puddings, &c. 

 After the fibrin is thus separated, the 

 blood no longer coagulates when allow- 

 ed to remain at rest, but a spongy, flaky 

 matter separates from it, and swims on 

 the surface. 



BLUE, otherwise called azure, is one 

 of the primitive colours of the rays of 

 light. 



BLUE, painters, is made different, ac- 

 cording to the different kinds of paint- 

 ing. 



In limning, fresco, and miniature, they 

 use indifferently ultramarine, blue ashes, 

 and smalt : these are their natural blues, 

 excepting the last, which is partly natural, 

 and partly artificial. 



In oil and miniature they also use in- 

 digo prepared ; as also a fictitious ultra- 

 marine. 



Enamellers and painters upon glass 

 have blues proper to themselves, each 

 preparing them after their own manner. 



BLUING of iron, a method of beautify- 

 ing that metal sometimes practised ; as 

 for mourning buckles, swords, or the 

 like. The manner is thus : take a piece 

 of grindstone and wetstone, and rub 

 hard on the work, to tuke off the black 



