454 
POPULAR SCIENCE REVIEW. 
in practice. The substance used is manganate of soda, which M. de Motay 
hopes to be able to sell to the trade at fourpence per kilogramme. Fifty 
kilogrammes of manganate give, according to calculation, from 400 to 450 
litres of oxygen per hour. 
An Illustration of the Manufacture of Sulphuric Acid, which is very simple, 
and may be found useful by lecturers as an experiment, has been described 
by a correspondent of the Chemical Neivs. It is a modification of an experi- 
ment described by Dr. Miller. Three tubes are passed through the cork 
of a wide-mouthed bottle, the largest being connected by an india-rubber 
junction with a pint funnel, and the small one to the left with a test-tube 
generating NO by means of copper turnings and nitric acid. The middle 
tube admits air. A little water is poured into the bottle first, to combine 
with S0 3 for the production of H 2 S0 4 . The funnel is covered in with a 
metal cap, to which a small pan is suspended. This pan is a miniature 
furnace. A bit of sulphur is placed in it and lighted. The fumes of S0 2 
immediately flow down in a conspicuous stream into the bottle. Here they 
encounter NO, and the usual reaction takes place. Any S0 2 which the 
water may dissolve is expelled by boiling, when the solution answers to all 
the tests for the presence of sulphuric acid. An extra cover, which slides 
on the metal lid, conceals some air-holes, useful at the beginning of the 
experiment. 
The Estimation of Organic Matter in Water. — This is a subject of the 
utmost importance, and it is much to be regretted that it has not received 
the attention it deserves. At least we judge so from the fact that till 
recently we have had no reliable method of distinguishing between the 
organic matter present in water or ammonia and that present as excremen- 
titious substance. It has lately been shown by Messrs. Wanklyn and 
Chapman that the methods pursued by Drs. Frankland and Letheby hardly 
compass this end. These chemists have therefore suggested the employment 
of a new method of estimating organic matter. This method has been fully 
described in their joint paper, read before the Chemical Society on the 20th 
of June last; but the following account gives an idea of the nature of their 
method : — Direct experiments were made upon known quantities of urea, 
albumen, and gelatin dissolved in water, and the singular fact was disclosed 
that, whilst the first of these bodies is completely changed into ammonia by 
boiling with carbonate of soda, the two latter substances resist decomposition 
until caustic soda (or potash) is introduced, when one-third of the nitrogen 
contained in them is evolved in the form of ammonia. The remaining two- 
thirds of this constituent are finally liberated in the same form upon adding 
some crystals of the permanganate of potash and continuing the distillation. 
The authors employ Nessler’s test for indicating the proportion of ammonia 
originally contained as such in the water, as well as that subsequently 
formed. 
The Density of Ozone. — M. Soret, who sometime since stated the density of 
ozone to be 1 1 times that of oxygen, now has given convincing proof of the 
accuracy of his opinion. By causing the two bodies to u diffuse,” he has 
found that the velocities of transmission give the same value for the density 
of ozone as that already expressed, viz. times that of oxygen. 
Detection of Bromine and Iodine in same Solution. — A paper has been pub- 
