Technical Chemistry. . 427 
cent plus zinc 80 to rig per cent, is rendered softer, fons tenacious, and less dense by 
tempering it ;—a fact which Mallet* has very properly anes n explanation of the 
differences between several of the specific gravities of ‘a ltoys of copper and zine ob- 
served by himself, and a numbers which had been previously obtained by other 
en woul 
the sp 
himself.+ It is also the most probable explana tees oe the alloys of abnormal color 
which e has described. I should observe in this connection, that in the alloys of 
he i 
ae fits ‘be akes little no impre n upon the bites a reaute which 
agrees with those of Karsten$ of Mallet, | and. ‘of. Guettier.g] Calvert and John- 
son pte i a 
Vv : 
containing 54 per cent of copper, which is-still so tenacious that small bits a 
readily be broken from it, was found to be exceedingly difficult to cut with a 
chisel; for though still so soft that it coke be filed without any very great cabled, 
it ‘acest ont “ once the edges of cutting serene though the latter were well 
tempered. This peculiarity appears to ‘be connected with ihe fibrous structure of 
the alloy.” 
2. Preparation of Oxygen on the Great Scale. wed addition to the 
a q 
on page 280, Devitte and Desray have now published an elaborate ar- 
ticle containing the details of their labors upon this subject to which we 
would call the attention of technological chemists.. In this memoir, which 
forms a part of their remarkable monograph upon the metallurgy ‘of pla- 
tinum, &c., they have studied the comparative merits of all the industrial 
processes of manufacturing oxygen which were known ee and of 
the methods which they have themselves devised dere iew of ena- 
bling any manufacturer to decide which process m be best sited a rd 
locality or circumstances in which he happens to be situated. 
— ae a ethod of preparing oxygen from chlorid of time which 
o be well adapted for laboratory use-—when heated to low redness, 
chlorid of ime (bleaching powders) gives off, per pound, from twenty to 
t : hens ‘ " 
ter, the formation of this impurity may be prevented by adding enough 
slaked lime to the chlorid employed that this shall be strongly alkaline ; 
if this precaution be attended to, the operation may be conducted in iron 
vessels. It is of importance only to avoid heating the mass to the fusion 
t I have found it i ik he ob 
of this chemist, slthoogh it is oer clean that ih gre atest agin Akon tion is at a poin' 
some alloy compe equivalents of copper and zine, a ma 
between this point pe pure cope the pone gravity gradually increases with _— de- 
gree of regularity in proportion as the amount of copper increases Among the ubserved 
specific gravities of tbe white alloys rich in zinc, there is no larity whatsoever. The 
determinations of Mallet are, neve: ess, uestionabl best which have a 
pete made ; possibly ea are the best which could be ns any case. At all events, 
chemists are in t position to ca upon the method of preparing se aa which 
pete loyed by this di 
HS tar From th ‘this i gaegory as Save modified iy tempering must of course be excepted. 
; : ew Cit, = a a Gmelin’s fone peg haem Soc. Edit.,) v, 479. 
= 
