SCIENTIFIC SUMMARY. 109 
a similar reaction, but only after from twelve to twenty-four hours’ 
maceration in water. 
As bearing upon the above researches, it may be stated that Professor 
I G. C. Schaeffer has contested M. Schoenbein’s right to priority in putting 
forward the views we have alluded to. He states ( Silliman 7 s American 
Journal ) that in the annual report of the Smithsonian Institution for the year 
1861, a report appears on nitrification presented to the institution in 1856, 
by Dr. B. F. Craig, from which the following passage is extracted : — • 
“ This action takes place very commonly with those substances which are 
produced from ammoniacal salts by the separation of the elements of 
water, and may be effected under the influence either of acids or alkalies, 
and sometimes by the action of water alone at very high temperatures 
In the case of nitrogen it may be represented thus : — ■ 
N 3 -fH 4 0 4 =N0 4 NH 4 ” 
Quantity of Carbonic Acid in the Atmosphere . — M. Mene has addressed 
a note to the “ Academie des Sciences ” upon this subject. He gives the 
following as the results of his analytical investigations : — 
1st. That the quantity of carbonic acid contained in the atmosphere 
is variable. 
2nd. That there is nearly an equal quantity of carbonic acid present 
during the months of December and January ; that this gas increases in 
February, March, April, and May, but diminishes from June to August ; 
that it again increases from September to November, attaining its 
maximum for the year in October. 
3rd. That there is always more carbonic acid present during the day 
than during the night. 
4th. There appears to be some oscillation as to the quantity of this 
gas during the day ; this takes place about noon, when a slight increase 
is observed. 
5th. That after rain carbonic acid is always more abundant than 
before it. 
The Detection of Wood-spirit in Essences , Tinctures , fyc. — It is well 
known that in certain cases essences and tinctures are prepared with this 
spirit instead of pure alcohol, hence it becomes necessary that we devise 
some means of detecting the fraud. “ Ure’s test ” is that which is usually 
adopted ; it consists in adding powdered hydrate of potash to the sus- 
pected liquid, when if a brown colour be produced wood-spirit is said to be 
present. Mr. E. J. Reynolds ( Dublin Quarterly Journal of Science, July) 
shows that this test is fallacious in some instances, owing to the circum- 
stance that some of the volatile oils pass over in distillation and give 
rise to a distinctly brown tint with caustic potash in powder. He pro- 
poses the substitution of the following test : — “ A small quantity of the 
suspected liquid is placed in a tube-retort and distilled over into a cooled 
test-tube ; two or three drops of a very dilute solution of chloride of 
mercury are now added to the distillate and then excess of solution of 
caustic potash, and the whole well shaken. If the precipitated oxide of 
mercury do not re-dissolve even on warming the liquid, wood-spirit is 
not present.” 
