Chemical Science. 187 



The points of fusion of the alloys of tin and lead, which have 

 served for the foregoing experiments, are as follow : — 



Lead .... 334° 



Tin . . . .230 



5 atoms of tin, 1 atom of lead . 194 



4 atoms of tin, 1 atom of lead . . 189 



3 atoms of tin, 1 atom of lead . 18o* 



2 atoms of tin, 1 atom of lead . . 196 



1 atom of tin, 1 atom of lead . 241 



1 atom of tin, 3 atoms of lead . . 289 



2 volumes of tin, 1 volume of lead . 194 



25. On a peculiar Principle in Blood, distinctive of its Source. — 

 This principle has been remarked and described, and its utility in 

 medical jurisprudence stated by M. Barruel. Whilst preparing the 

 colouring matter of blood according to M. Vauquelin's process, the 

 clot of ox blood was boiled with a large excess of sulphuric acid of 

 moderate strength, on which occasion a strong odour of beef was 

 observed. Some time after, having occasion to operate upon the 

 blood of a man who had taken opium, the fluid was first coagulated 

 by heat, and divided, after which it was boiled with weak sulphuric 

 acid : immediately so strong an odour of the sweat of man was 

 evolved as to infect the whole laboratory, and render it necessary 

 for the persons to leave the place. This and the former fact com- 

 bined, induced M. Barruel to extend experiments on these subjects, 

 and the following are the results. 



i. The blood of each species of animal contains a principle 

 peculiar to each. ii. This principle, which is very volatile, has an 

 odour resembling that of the sweat, or the cutaneous, or pulmonary 

 exhalation of the animal from which the blood was taken, iii. In 

 the blood this volatile principle is in a state of combination, its 

 odour being then insensible, iv. When the combination is broken, 

 this principle is volatilized, when it is easy to recognize the animal 

 to which it belongs, v. In each species of animal, this principle 

 is more decided, or has more intensity of odour in the male than in 

 the female ; and in men, the colour of the hair accompanies 

 certain variations in this principle, vi. This principle is in a soluble 

 state in the blood, and may be found, therefore, either in the un- 

 altered blood, or after the fibrine has been removed, or even in the 

 serosity of blood, vii. Of all the means of setting this principle 

 at liberty concentrated sulphuric acid has succeeded best. 



To obtain these results, it is only necessary to put a few drops of 

 blood or the serosity of blood iuto a glass, to add concentrated sul- 

 phuric acid, to the amount of one third or half as much as of blood, 

 and to stir the whole together with a tube — the odoriferous principle 

 is immediately rendered evident. By these means, M. Barruel 

 can readily distinguish the blood from the following sources. 



i. That of a man disengages a strong odour of the perspiration 



