.202 
POPULAR SCIENCE REVIEW. 
•forward in tlie daily papers, I condensed water containing oxygen upon the 
metal and tlie subsequent formation of the insoluble hydrocarbonate, and 
there can be little doubt that water drawn from such a cistern would be 
contaminated with lead.” 
Absorption of Gas by Iron Wires. — The absorption of gas by these when 
re-heated to redness, and then quenched in dilute sulphuric acid, is the subject 
of an important paper in a late number of the u Comptes Rendus,” by M. D. 
Sevoz. It seems that in wire-drawing, when the maker has arrived at a 
•certain gauge, he is obliged, in order to draw the wire finer, to re-heat to 
redness in cast-iron stoves, closed as hermetically as possible, and then to 
quench in water containing 2-3 per cent, of monohydrated sulphuric acid. 
It often happens that iron wire which has undergone these two operations, 
for instance, at No. 18 (34-10ths of a millimetre), becomes brittle when it has 
reached No. 8 (13-10th). If the wire is broken, and the fracture plunged 
into a glass of water, rapid and numerous bubbles of gas are seen to escape. 
The author has collected this gas, mixed it with air, and obtained a distinct 
explosion, but has not been able to decide whether it is carbonate oxide or 
hydrogen. The presence of a small quantity of this gas renders the metal 
brittle. When the wire-drawers meet with pieces of brittle wire they 
ascertain, by putting saliva upon the fracture, whether the brittleness is due 
to gas. If this is the case they lay the wire aside for five to eight days, 
when the gas is found to have disappeared, and the wire resumes its ordinary 
malleability. 
Certain Properties of Weighted Black Silks. — The u Chemical News ” 
•of February 3, in noticing a paper of M. Persoz, says that the author shows 
that weighing — which began with the modest aim of making up the loss 
sustained in ungumming — is now carried to the extent of 100, 200, and 300 
per cent. This increase of weight is produced by treatment with salts of 
iron and astringents, salts of tin and cyanides. The bulk is augmented pro- 
•portionably to the weight. As a matter of course, the chemical and 
^physical properties of the silk thus treated are materially modified. What 
is sold as silk is, in fact, a mere agglomeration of heterogeneous matters, 
devoid of cohesion, held temporarily together by a small portion of silk. 
The elasticity and tenacity of the fibre are sensibly reduced. From being in 
its natural state one of the most permanent of organic bodies, and sparingly 
combustible, it burns like tinder if touched with flame. It is, moreover, liable 
to undergo spontaneous decomposition, and to absorb gases with the evolu- 
tion of heat, which sometimes leads to actual combustion. The adulterated 
silk when burning scarcely gives off the characteristic odour of animal 
matter. It leaves an ash of oxide of iron, exceeding 8 per cent. 
Gold-lined Capsules and Crucibles , a cheap way of making. — Mr. J. L. 
•Smith, of the United States, makes the following remarks in a paper on 
various subjects that he has communicated to the “ Chemical News ” 
'(Feb.). He says : u While the analytical chemist cannot always indulge in 
every form of luxury of apparatus which might tend to facilitate and give 
precision to his researches, still they are very convenient and useful at times. 
Those who have had much to do with caustic potash and nitre heated to 
redness, know that silver vessels will not always answer their purpose. 
Under these circumstances gold vessels are very useful, but very expensive, 
