238 
POPULAR SCIENCE REVIEW. 
a glass globe. The latter has an aperture on one side opposite to the flame, 
which allows the radiation to pass unchanged into a brass experimental tube, 
which is fixed horizontally in front of the lamp. The radiation from the 
flame, after passing through the experimental tube (which has been pre\dously 
thoroughly exhausted of air) falls on a thermo-electric pile and deflects the 
needle of a suspended and delicate galvanometer. In the next instance this 
deflection is neutrahzed, by placing before the opposite face of the pile a 
cube containing water kept boiling, and also by the careful adjustment of a 
double metal screen. If an absorbent gas is now admitted into the tube, 
the balance is disturbed, and the needle is deflected in proportion to the 
absorbing power which the gas possesses. In this way the portion of the 
arc through which the needle travels, indicating the extent of the disturbing 
power, enables the observer to calculate the per-centage of the gas present. 
Should this discovery be capable of practical application, it would be of 
immense advantage to have a machine upon this principle attached to all 
hospitals for diseases of the chest, as by its means the physician would be 
enabled to perceive some important phenomena in connection with the 
function of respiration, which, were an ordinary analysis necessary, would be 
placed quite beyond his reach. We understand that from one experiment, 
Messrs. Tyndall and Barrett ascertained that the air of their laboratory, 
compared with that from the Downs of Brighton, possessed an excess of 
absorbing power which was equivalent to four per cent. 
The Extraction of the Aromata of Floivers . — At the autumn meeting of the 
Pharmaceutical Conference, an interesting communication was read by 
Mr. R. C. Tichborne, upon the best means • of preserving the odorous 
principles of flowers. Having observed the faculty which glycerine possesses 
of preserving vegetable as well as animal substances, he packed different 
kinds of scented flowers in jars and covered them with this fluid. Some 
specimens were kept in this way for two years, and when the glycerine was 
removed, it was found that the volatile oils had been extracted by it, and on 
distilling it a liquid vastly superior to the ordinary “ water ” was obtained. 
Mr. Tichborne recommends the following as the best process for the removal 
of the volatile oils ; — After macerating the flowers for some considerable 
time in glycerine, the latter is expressed and is again treated with fresh 
flowers, until the excipient is thoroughly saturated with the otto (the 
extraction appears to be complete, as the glycerine has a decided affinity 
for the volatile oils). The saturated glycerine is then diluted with water, 
and shaken with a small quantity of chloroform. After frequent agitation, 
the latter is allowed to subside, when it is found to have carried 
down with it nearly the whole of the essential oils. This chloroform 
solution, after being separated by a funnel, should be filtered and allowed 
to evaporate spontaneously in a shallow vessel ; the residual matter 
when dissolved in spirit forms the spirituous extract of the flowers. 
When operating upon large quantities of flowers, it becomes necessary, for 
economy’s sake, to drain off the greater portion of the chloroform by means 
of a still. This does not injure the extract, because the boiling point of the 
chloroform is very low. The glycerine may be used over and over again, 
by diluting it, passing it through charcoal, and finally evaporating it till it 
attains its proper specific gravity. 
