204 
POPULAR SCIENCE EEYIEW. 
the carbonic acid from a known volume of air, the excess of baryta beinsr 
ascertained by tbe use of a standard solution of oxalic acid. Mr. Thorpe’s 
first experiments were made in tbe Irish Sea, in August, 1865, on board tbe 
“Bahama Bank ” light ship, which is situate seven miles from Douglas, Isle 
of Man, and consequently about equidistant from the shores of England, 
Scotland, and Ireland. The results and meteorological conditions are given 
in the form of a table, wherein it is seen that there is no perceptible varia- 
tion in the amount of carbonic acid during the day and night, the hours of 
4 a.x. and 4 p.ir. having been selected for the observations, these times 
coinciding with the maximum and minimum temperatures. Similar ex- 
periments were made last year in many latitudes of the Atlantic Ocean 
during voyages to and from the Brazils. The results are nearly identical 
with the former, and the amount of carbonic acid is said to be 300 parts in 
10,000 of air, as the general average of the whole series of seventy-seven 
observations. 
A Test for Wood-fibre in Paper has been suggested byM. Behrend. The 
suspected paper is touched with strong nitric acid. The presence of wood 
is indicated by the paper being turned brown, especially on the application 
of heat. This test is said to be more certain than the sulphate of aniline 
one. 
The Determination of the Nitrogen in Ammoniacal Salts. — Herr Knops’ 
method, which is a modification of Herr Wohler’s, which consists in treat- 
ing ammoniacal salts with bleaching powder, has been highly spoken of by 
M. Dietrich. According to an account in the Philosophical Magazine for 
February, the decomposing solution is prepared by precipitating good 
bleaching powder with carbonate of soda, and adding two to three grammes 
of bromine to a litre of the solution after it has been made strongly alkaline. 
Its strength is then estimated by a standard solution of arseniate of soda. 
Fifty cubic centim. of this solution had the power of liberating 200 milli- 
grammes of nitrogen. For the determination, 50 cubic centim. were 
always taken, and substance always dissolved in 10 cubic centim. of water, 
or stirred up with it, in case it was insoluble. Making the usual correction 
for the volume used off, and allowing for the gas which remained in solution 
in the liquid, M. Dietrich obtained very accurate results with this process 
of Wohler and Knops. 
The Reducing Action of Zinc has been recently studied by Herr Stahl- 
schmidt, who has published a paper on the subj ect in Poggendorff s Annalen. 
In the presence of a soluble alkali, finely divided zinc reduces nitrates to 
nitrites in the most rapid manner. Hence, as has been suggested, zinc may 
be employed for the conversion of the former into the latter. Commercially, 
it may be obtained at a cheap rate. It is to be found in all zinc- works, and 
consists of — zinc, 39-99 ; lead, 2-47 ; cadmium, 4*09 ; oxide of zinc, 49-76 ; 
and carbonate of zinc, 3-29. Washing this crude powder in acids is all 
that is required to prepare it for the reduction of nitrates. 
u The Laboratory ,” a new chemical and physical journal is, we believe, to 
make its appearance on the 5th of April. Its name affords a clue to the 
nature of the subjects on which it will treat. We trust the new venture 
may be a successful one, but we fear the commercial experience of those 
who have had to do with new technical and “ class,” scientific periodicals is 
