2 Occult Blood in Stools 
All the above objections can be overcome by the use of guaiac- 
onic acid which is the active agent of the gum. ‘The preliminary 
work of this investigation was carried out with Mertk’s guaiaconic 
acid; but as this reagent was difficult to purchase, and its cost 
high, we experimented with gum guaiact in the hope of preparing 
therefrom some substance which in keeping qualities and sensi- 
tiveness would be fully equal to the commercial preparation of 
gualaconic acid and, moreover, would possess the additional merit 
of being readily and economically prepared. This we succeeded 
in doing. 
Preparation of the Reagent. 
The method of preparation based on a series of preliminary 
experiments’ is as follows: 50 gm. of the ground crude gum guaiac 
were treated in a beaker with 20 gm. of KOH dissolved in 200 ec. 
' of water. After thorough stirring, the mixture was filtered with 
the aid of suction through cotton spread out in a thin Jayer in a 
Buchner funnel. The residue was washed with water until the 
combined filtrate and washings approximated 1.5 liters. To the 
diluted KOH solution were added with constant stirring 21 ce. 
of glacial acetic acid which was run dropwise from a burette. 
The precipitate was allowed to settle, the supernatant liquid 
poured off, and the residue washed once with water by decanta- 
tion. The precipitate was then transferred to a Buchner funnel 
and dried by suction as much as possible. The precipitate was 
gently heated (small portions at a time) in an evaporating dish 
when most of the water separated and was removed by filter 
paper. After the removal of the water, and while the mass was 
still plastic, it was drawn out into thin sheets. In this condition 
the material rapidly hardens and dries in the air. The dried 
masses were then ground, treated with 300 cc. of hot 95 per cent 
alcohol and the mixture was thoroughly stirred to prevent the 
formation of a gummy mass. In a few minutes a dark brown 
material separated in a flocculent condition. This was filtered 
color but of short duration. Under the same conditions, our preparation 
gave a good blue color which lasted for some time. The experiment was 
repeated with the same results. 
3 We wish to acknowledge the assistance of Mr. A. G. Wikoff i in the prep- 
aration of this substance. 
