CHEMICAL TESTS FOR BLOOD. 
By Joseph Hoeing Kastle, Ph. D., 
Chief of Division of Chemistry, Hygienic Laboratory, U. S. Public Health and Marine- 
V Hospital Service. 
The greater number of strictly chemical tests for blood in use at 
the present time depend on the power of blood to induce the oxida- 
tion of various chromogenic substances by means of various oxidiz- 
ing agents of the type of hydrogen peroxide. In such tests the blood 
plays the part of an oxygen carrier. In the clinical examination for 
blood and in forensic investigations a considerable number of chro- 
mogenic substances have been emplo 3 md, such as guaiacum, aloin, 
the leuco base of malachite green, benzidin, phenolphthalin, etc., as 
well as various oxidizing agents, such as ozonized oil of turpentine, 
hydrogen peroxide, etc. When small amounts of aiw one of these 
chromogenic substances are brought together with water and h}"dro- 
gen peroxide or ozonized oil of turpentine and a minute quantity of 
blood, a colored substance is produced the nature and color of which 
depend, of course, on the nature of the chromogenic substance 
employed. Property controlled, the development of such a color 
under these conditions indicates blood, and certainty if no color devel- 
ops it indicates the absence of blood. 
The historical development of this subject forms one of the most 
interesting chapters in the histoiy of clinical chemistiy. 
The fact that blood has the power to blue guaiacum in the pres- 
ence of ozonized turpentine or ly^drogen peroxide was first pointed 
out by Schoenbein in 1856. In a communication on ^ ^Chemical Con- 
tact Actions” (149) he describes the remarkable effect of certain 
substances on such compounds as hydrogen peroxide, old oil of tur- 
pentine, and ozonized ether, as a result of which the inactive oxygen 
which they contain is either set free or converted into ozonized 
(active) oxygen. He had previously shown that ozone and the so- 
called ozonids have the power of bluing the tincture of guaiacum, 
whereas pure hydrogen peroxide and other antozonids can not effect 
Manuscript submitted for publication April 27, 1909. 
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