8 
4. If a residue remains, add to the glycerin some distilled water and several drops 
of ammonia to determine the presence of lime. 
5. A drop of solution of sulphhydrate of soda should not produce a color in 
glycerin, but throws down a black precipitate if it contains lead or iron. 
6. For glucose, treat the glycerin with Fehling’s solution, using the usual precau- 
tions to obtain the reduction of the copper. 
7. The presence of chlorids in glycerin is indicated by silver nitrate. Pure glyc- 
erin will show neither opalescence nor precipitates. 
8. Tribasic acetate of lead added to glycerin diluted with distilled water produces 
a limpid solution. A precipitate or a cloudiness indicates the presence of fatty acids. 
9. Mix equal parts of glycerin with sulphuric acid. If carbon-dioxid gas is given 
off it contains oxalic or formic acid. 
10. Mix the glycerin with pure alcohol and a little sulphuric acid. An odor of 
jineapple is immediately developed, due to butyric ether (butyric acid). 
11. Glycerin heated to 120° should show no color. 
12. For arsenic, test by means of Marsh’s apparatus. 
ACKNOWLEDGMENT. 
It is a pleasure to acknowledge the faithful assistance rendered by 
my assistants in the laboratory in working out some of the details of 
this study upon glycerin, especially to Drs. John F. Anderson, T. B. 
McClintic, Allan J. McLaughlin, and Edward Francis. 
ANTISEPTIC POWER OF GLYCERIN. 
The first series of experiments were made in order to determine 
the antiseptic properties of glycerin; that is, its power to restrain 
the growth and development of bacteria. This was tested by deter- 
mining the amount of glycerin necessaiw to add to nutrient bouillon in 
order to prevent putrefaction, and the amount necessary to prevent 
the growth and development of pure cultures of various organisms. 
Erlenmayer fiasks of 100 c. c. capacity were partly filled with the 
bouillon-glycerin solution. The flasks were then contaminated with 
various substances, such as rich, black garden earth, wisps of ha}^ or 
fresh stable manure. 
The flasks were allowed to remain in a dark corner of the laboratory 
at room temperature, and results noted. 
More or less growth of bacteria and mold was obtained in all the 
flasks containing 10 per cent of glycerin. Those containing 50 per 
cent or over remained clear and showed no growth. Therefore, it 
was plain that the antiseptic power of glycerin lies somewhere between 
10 and 50 per cent. 
The next series of flasks contained various percentages of glycerin 
between 10 and 50 and were inoculated in the same way, in order to 
determine more definitely the exact percentage of glycerin necessary 
to restrain growth and development of micro-organisms. 
