400 Analysis of Scientific Books. 



fallen, and to advertise him of two or three samples of bad 

 taste which have probably escaped his notice ; ui>on these 

 heads we propose to be very brief. 



The hydrocyanic, or prussic acid, in its dilute state, was first 

 separated from Prussian blue by the celebrated Scheele, who 

 obtained it in the form of a colourless transparent liquid, having 

 in an eminent degree the odour of bitter almond, in which, as 

 well as in the cherry-laurel, the leaves and kernels of the peach, 

 and several other vegetable products of the same odour, the 

 same principle has been shown to exist : some of our less che- 

 mical readers may, perhaps, also remember its presence in 

 Noyau, Maraschino, and certain other species belonging to that 

 genus of liqueurs. 



For our knowledge of the real nature of the prussic acid, we 

 are indebted to the admirable researches of Gay-Lussac, He 

 has shown its base to be a peculiar inflammable gaseous com- 

 pound of carbon and nitrogen, on which he has conferred the title 

 of cyanogen, a term derived from the Greek, and signifying the 

 producer of blue ; whether, because it burns with a blueish purple 

 flame, or because it is essential to the production of the pigment 

 called Prussian blue, or for both reasons, we are not quite clear : 

 this cyanogen, however, combined with hydrogen, he has shown 

 to produce the prussic acid, which he accordingly terms hydro- 

 cyanic acid. It is a highly-volatile liquid, lighter than water, 

 and becoming concrete when exposed to the air, in consequence 

 of the cold generated by its rapid evaporation ; its odour is 

 similar to that of Scheele's acid, but infinitely stronger ; and it 

 is so deleterious in its action upon the living frame as to oc- 

 casion the death of large animals in the dose of a drop or two 

 only, and even to excite very disagreeable sensations in the 

 human body when its vapour is inhaled, largely diluted with 

 atmospheric air. 



It is a curious but correct axiom, that the more mischievous 

 the qualities of a substance are, the more likely is it to prove 

 of value in the Materia Medica ; and, when properly diluted by 

 or blended with other remedies, to become of importance in the 

 practice of physic. Accordingly, formidable as the prussic 



