316 
POPULAR SCIENCE REVIEW. 
that (“ Comptes Rendus,” March 29) potassium, sodium, and palladium 
combine with hydrogen, whilst a considerable number of other metals 
merely dissolve this gas. Iron, nickel, cobalt, and manganese offer striking 
analogies in the manner in which they behave with hydrogen at different 
temperatures. The facility with which they absorb or give off hydrogen 
gas depends greatly on their physical condition. An ingot of pure nickel 
gave out, in a vacuum, at a red heat, one-sixth of its volume of hydrogen. 
Laminse of nickel, obtained electrolytically, gave out forty times their 
volume. Pulverulent nickel gave out one hundred times its volume, and 
remained pyrophoric after the escape of the hydrogen. An ingot of cobalt 
gave out one-tenth of its volume, electrolytic laminse of cobalt thirty-five 
times their volume, and pyrophoric cobalt powder one hundred times. It 
also remained pyrophoric after the loss of the hydrogen. Soft iron in 
ingots gives off one-sixth of its volume, and grey cast-iron more than the 
half. Electrolytic laminse of iron gave off 260 volumes. In fine, it may 
be said that iron, nickel, and cobalt absorb directly hydrogen gas, but it 
•cannot be said that combination ensues, just as has been already shown in 
the case of lithium and thallium. 
Carbonic. Acid in the Air. — In the recent balloon ascent in the “ Zenith ” 
by M. G. Tissandier, that gentleman examined the amount of carbonic acid 
present in the air. At the altitude of 800 to 890 metres, at the temperature 
of 0°, and the pressure pf 760 m.m., the amount of carbonic acid in 10,000 
parts was 2-40. At 1,000 metres the proportion was 3*00. These differences 
are within the limits of variation of experiments made on the surface of the 
earth. — Comptes Rendus, April 12. 
Pecidiar polarisable Substances normally found in Wine. — The 11 Chem. 
News ” for April 12 gives a note on a paper by M. Bechamp recently read 
before the French Academy. It says that wine decolourised, suitably 
concentrated, and freed from tartar, yields a solution which, in some cases, 
turns the plane of polarisation to the left, in some to the right, and in 
others occasions no deviation. When it turns to the left it is because the 
quantity of non-crystalline sugar is more than sufficient to compensate for 
the effect of the dextro-gyratory matters. When it turns to the right, the 
quantity of lsevulose is too small to compensate the action of the dextro- 
gyratory matters, or else it has been entirely destroyed. If there is no 
deviation, the dextro-gyratory matters are exactly compensated by the 
lsevulose, or all the active matters have disappeared. Neither the sacchari- 
meter nor the cupro-potassic reagent are safe processes for the determina- 
tion of the sugar in wines. Hence, fermentation alone appears trustworthy. 
Detecting Lead in the Tin Lining of Vessels. — M. Fordos has given a new 
and rapid process for the above in a paper read before the French Academy 
(March 29, 1875). He says : “ Place, with a tube plunged in pure nitric acid, 
a slight layer of acid upon any part of the tinning, selecting by preference 
the thickest parts. Both metals are attacked, forming stannic oxide and 
nitrate of lead. After a few minutes heat slightly to expel the last traces 
of acid, and allow to cool ; then touch the pulverulent spot produced by the 
acid with a tube dipped in a solution of 5 parts of iodide of potassium in 
100 of water. The iodide has no action upon the oxide of tin, but with 
the nitrate of lead it reacts, forming yellow iodide of lead, and showing the 
