282 THE AMERICAN MONTHLY [Sept 



can generate in these conditions seizable qi^antities of fer- 

 rous compounds. 



The above-described method of extraction of blood 

 stains with concentrated solutions of chloral hydrate 

 which, as is wellrknown by this time, are also good sol- 

 vents for resins, has induced some experiments in order to 

 ascertain whether, by using the process mentioned in the 

 fitst part of this essay, chloral solutions containing blood 

 and guaiacum may, by precipitation with water and sub- 

 sequent filtration, give a resinous secretion containing 

 blood constituents, showing the mentioned behavior and 

 applicable to the guaiacum-blood-reaction after any time 

 of conservation. It may here be stated, by the way, that 

 the trials performed in this manner have but led to a mod- 

 erately satisfactory result, probably because even a 

 diluted chloral-solution still acts as a solvent on the resin 

 in a low, but perceivable degree and besides, as I am in- 

 duced to believe, because the coloring matter of blood is 

 less easily precipitated by the secreting resin from a 

 chloral-blood-solution than from a chiefly aqueous liquid. 

 But, notwithstanding the loss of material caused in that 

 way, by. the use of this method resin-covered filters can 

 be obtained possessing the properties quoted in the be- 

 gining of this paper. 



Lastly, it may be mentioned that — as it could be ex- 

 pected — the guaiacum blood-test executed with chloral 

 solution is thoroughly applicable to a control-reaction, 

 viz., to the chemicalidentification of the hemin-crystals, 

 which are of high importance injudicial cases. A specially 

 pure blue coloration is obtained, when, instead of the or- 

 dinary guaiacum-solution of guaiaconicacidin 200 to 500 

 parts of chloral-solution (v. s.) is used, and the reaction 

 is observed in a glass tube as a zone-reaction. The 

 guaiaconic acid, proposed as a substitute for the natural 

 resin by 0. Doehner in his interesting essay on guaiacum 

 resin and ''guaiacum-blue," is just as well liable to spon- 



