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R. P. HIBBARD 
washed, thoroughly steamed and finally rinsed with the test water 
before being used in the experiment. The growth rate was chosen as 
the criterion. The control solution was tap water. This was allowed 
to run freely from the faucet for at least 15 minutes so as not to use 
the water that had rested in the supply pipes. It wafe then collected 
in clean Jena glass flasks and put aside near a radiator to come quickly 
to the room temperature, the temperature at which the distilled water 
was maintained. The cultures were set aside on a table away from 
the windows and covered with paper. 
Preparation of Distilled Water 
Only water which was prepared in contact with laboratory air of 
average purity is to be here considered. Absolute water prepared 
and used in vacuo^; water obtained by the combination of oxygen 
and hydrogen in the presence of an electric spark^ or water distilled 
from a quartz distilling apparatus in contact only with air from out- 
of-doors dried and rid of CO2 by the usual methods, is not here used. 
A comparative study of all the available methods was made. Various 
combinations were used for the purpose of eliminating this or that 
source of trouble. In all twenty-six methods were tried. Livingston^^ 
showed that good water could be obtained by shaking distilled water 
with finely divided carbon black. By a process of adsorption both 
volatile and non-volatile substances toxic in nature are taken up. 
E. P. Lyon^^ obtained water of excellent quality by adding a little 
H2SO4 to the tap water in an automatic still consisting of a copper 
vessel and glass condenser, providing none of the condensed water 
touched the metal. It is suggested that the volatile toxin, ammonia, 
is eliminated by the H2SO4 treatment. Hoyt^^ made an improvement 
on Livingston's method by distillation with animal charcoal in the 
retort. A combination of the last two with an additional treatment 
8 Kohlrausch & Heydweiller. Wied. Ann. 53: 209. 1894. 
^ Any of the good text-books on general chemistry. 
10 Method used in the research laboratory of physical chemistry, University of 
Illinois. Not yet reported. 
1^ Livingston, B. E., Jensen, C. A., Breazeale, J. F., Pember, F. R., Skinner, 
J. J. Further Studies on the Properties of Unproductive Soils. U. S. Dept. Agr. 
Bur. Soils Bull. 36. 1907. 
^2 Lyon, E. P. Biological Examination of Distilled Water. Biol. Bull. Marine 
Biol. Lab. 6: 198. 1904. 
" Hoyt, W. D. Some Toxic and Antitoxic Effects in Cultures of Spirogyra. 
Bull. Torrey Club 40: 338. 1913. 
