426 
POPULAR SCIENCE REVIEW. 
The gray tin, therefore, is somewhat passive. It is a curious fact that among- 
the gray rings contained in the wooden box were five rings having the 
colour and characters of ordinary tin. 
The Source of the Hippuric Acid in the Urine of Herbivorous Animals . — 
A number of chemists have taken up this question with little effect. Hall- 
wachs sought in vain for benzoic acid in hay, and found no substance in 
any way related to it. It is pointed out by Loew {Jour, prakt. Chem., 1879,. 
xix. 309), that Hallwachs did not search for ltinic acid, and that Lautemann 
has long since suggested that this substance may be present in hay, as it is 
pretty plentiful in the vegetable kingdom. This Loew now finds to be the 
case. If hay be moistened with cold water and allowed to stand for 24 
hours, and the contents be precipitated with lead acetate, and the well-washed 
precipitate be treated with sulphuretted hydrogen, a liquid is obtained 
which has now to be treated with milk of lime in excess to remove the 
phosphoric acid. The concentrated filtrate is then made hot, and while 
so, mixed with hot alcohol whereby the lime kinate is separated as a viscous 
mass. Further treatment consists in throwing down the lime with oxalic 
acid, and again adding alcohol to the concentrated liquid, whereupon the 
acidfseparates slowly in small granular crystals. Six grammes of kinate were 
obtained from one kilogramme of hay. "When distilled with manganese 
peroxide and sulphuric acid it evolved kinone. The kinates are very soluble 
in water, and readily precipitated by dilute alcohol. 
Action of Hydrogen on Carbonic Oxide in the Presence of a Red-Hot Plati- 
num Wire. — J. Coquillion has found when moist carbonic oxide is passed 
over a red-hot platinum wire many times backwards and forwards, a change 
of volume is noticed which, when the gas was shaken with potash, disap- 
peared, to appear again, however, as soon as the operation was renewed, 
until finally nothing is left but nearly pure hydrogen. The change noticed 
must take place in accordance with the equation — 
co+h 2 o=co 2 +h 2 . 
The presence of nitrogen does not interfere with the change. The con- 
version of carbonic oxide into carbonic acid, during the decomposition of 
water vapour, cannot take place all at once, for between the 00, C0 o , H and 
H 2 0, a state of equilibrium is set up, which limits the action. A moist 
mixture of 31 ’50 volume per cent, of carbonic oxide, 8 ’08 per cent, of 
hydrogen, and 60-42 per cent, of nitrogen, increased in volume 10 per cent., 
and was changed into 21 ‘3 per cent, of carbonic oxide, 10-00 per cent, of 
carbonic acid, 18-08 per cent, of hydrogen, and 60-62 per cent, of nitrogen. 
Pure carbonic oxide increased 30 per cent, in volume, and the mixture con- 
sisted of carbonic acid 30 per cent., hydrogen 30 per cent., and carbonic 
oxide 70 per cent. The author made these experiments during some inves- 
tigations of the gas found in Siemens’s generative furnaces. They were fed 
with coke, and it was not possible to convert the whole carbonic acid into 
carbonic oxide, however high the layer of ignited coke be made. The 
vapour of water contained in the latter takes part in the reaction by reoxi- 
dizing the carbonic oxide. The greater its quantity the higher rose the 
percentage of carbonic acid and of hydrogen. This reaction takes place- 
in smelting furnaces. Ebelmen held that hydrogen acted directly as coke. 
