MICEO-CHE3IICAL ANALYSIS 



I 103 



has been made in. connection with the detection of poisons, and by 

 a judicious combination of microscopical with chemical research, 

 the application of reagents may be made effectual for the de- 

 tection of poisonous or other substances in quantities far more 

 minute than have been previously supposed to be recognisable. 

 Thus it is stated by I)v. Wormley l that micro-chemical analysis 

 enables us by a very few minutes' labour to recognise with un- 

 erring certainty the reaction of the iooVoo tn P art f a grain of 

 either hydrocyanic acid, mercury, or arsenic ; and that in many 

 other instances we can easily detect by its means the presence of 

 very minute quantities of substances, the true nature of which 

 could only be otherwise determined in comparatively large quantity,, 

 and by considerable labour. This inquiry may be prosecuted, how- 

 ever, not only by the application of ordinary chemical tests under 

 the microscope, but also by the use of other means of recognition 

 which the use of the microscope affords. Thus it has been shown that 

 by the careful sublimation of arsenic and arsenious acid, the subli- 

 mates being deposited upon small discs of thin glass, these are dis- 

 tinctly recognisable by the forms they present under the microscope 

 (especially the binocular) in extremely minute quantities ; and that 

 the same method of procedure may be applied to the volatile elements* 

 mercury, cadmium, selenium, tellurium, and some of their compounds, 

 and to some other volatile bodies, as sal-ammoniac, camphor, and 

 sulphur. The method of sublimation was afterwards extended to the 

 vegetable alkaloids, such as morphine, strychnine, veratririe, 2 &c. 

 And subsequently it was shown that the same method could be further 

 extended to such animal products as the constituents of the blood 

 and of urine, and to volatile and decomposable organic substances 

 generally By the careful prosecution of micro-chemical inquiry, 

 especially with the aid of the spectroscope (where possible), the 

 detection of poisons and other substances in very minute quantity 

 can be accomplished with a facility and certainty such as were 

 formerly scarcely conceivable. 



1 Micro-chemistry of Poisons, New York, 1857. 



a See Wynter Blyth, Poisons, their Effects and Detection, London, 1895. 



