278 THE AMERICAN MONTHLY [Sept 



control reaction, inasmuch as the casual presence of ni- 

 trites (as, for instance, nitrite of ammonia) in the respec- 

 tive stain would at once cause a more or less intense blue 

 coloration of the mixture owing to the decomposition of 

 these salts by the acetic acid, the nitrous acid coloring 

 guaiacum, viz., guaiaconic acid blue even in high dilu- 

 tions. Moreover, if the chloral extract of the stain con- 

 tains only blood, the addition of the brownish-yellow 

 guaiacum chloral solution to the pale red liquid derived 

 from the stain will give a pale brown mixture exceeding- 

 ly well adapted for a decisive zone reaction indicating the 

 presence of hematin. To this blood guaiacum solution in 

 aqueous chloral hydrate a stratum of the already men- 

 tioned turpentine solution of Hunefeld or of an adequate 

 solution of hydric peroxide [the indifference of which to- 

 wards guaiacum, tincture being previously stated) is care- 

 fully added without mixing ; then an intensely blue and 

 rapidly increasing zone appears, with extraordinary sen- 

 sibility, in the place of contact and diifusion of the two 

 solutions, while by sudden mixture a less pure blue color- 

 ation of the liquid results. The method may also, in 

 suitable cases, be so modified that the blood solution is 

 first mixed with HunefeWs liquid and then added to the 

 guaiacum solution. This process can just as well be con- 

 ducted to obtain a zone reaction or also a capillary re- 

 action. 



In cases of extraordinary small blood stains, so as to 

 necessitate, in a certain measure, a microchemical opera- 

 tion, or where the respective residue of blood has to be 

 tested on its natural place, it is advisable to dtgest the 

 stain on a flat porcelain dish with strong chloral solution 

 (v. s.), having first moistened with a small drop of acetic 

 acid, and, after an hour's contact, to pour on the digested 

 spot first a corresponding small quantity of guaiacum 

 chloral solution, and then, after having thoroughly mix- 

 ed, a few drops of the one or other liquid containing the 



