/ 
MICRO-CHEMICAL REAGENTS. 27d 
Hardened masses of resin, such as are frequently found in- 
older drugs, often resist for a long time the action of the solvent,. 
a fact which must be considered in order to avoid incorrect con-- 
clusions. An alcoholic solution of caustic soda often has a bet-- 
ter action than alcohol and other solvents. 
20. Paraffin of a low boiling point (55 to 75° C.), the s0- 
called petroleum ether or petroleum benzin. This liquid serves 
for similar purposes as ether, benzol, and chloroform; it has, 
however, a much less energetic solvent action upon resins. 
21. Fatty Oil (Almond Oil is the best) is employed with ad- 
vantage as a mounting medium, when, beside the fatty oil 
occurring in the cells, it is desired to examine the other con-- 
stituents which would become decomposed or dissolved by glycerin: 
or water (aleurone). Sections of seeds rich in oil, when placed! 
in the fatty oil, appear very much clearer, since the oil is taken 
up by the mounting liquid. 
22. Liquid high-boiling Paraffin (Parafinwm lMquidum* 
of the Pharmacopoea Germanica), serves in most cases the same 
purpose as the fatty oil and is cleaner in its application. 
23. Todine in the form of powder, when strewn upon moist- 
ened sections, often produces purer colorations than iodine 
solutions; the excess of iodine is easily washed away with water.. 
Powdered iodine readily cakes together. It is therefore more: 
convenient to use it in form of a trituration with siliceous earth 
or pumice stone, and to preserve it in this form, since the latter 
substances are not objectionable in many of the reactions to be- 
made with iodine. 
With regard to the application of iodine and its solutions for: 
the recognition of starch, cellulose, and protein substances, com- 
pare the respective sections preceding. 
24, Iodine Water. One part of iodine shaken with 4,000: 
parts of water is used as a reagent for starch and those forms of” 
cellulose which show a similar reaction. 
25. Iodine Solution (Iodine with Poiana Iodide) is a. 
1 A clear, oil-like liquid obtianl from petroleum, free from colored,, 
fluorescent, and odorous substances. F. B. P. 
