730 
composition. Thus in copper-tin alloys 
rich in tin, erystals are found of the com- 
position (approximate) Cu Sn, Cu, Sn, and 
Cu, Sn, according to the amount of copper 
present, the first mentioned separating from 
an alloy with 2% copper. In ternary alloys 
it has been found possible to detect two, 
and sometimes three, distinctly different 
compounds in the same microscopic field. 
The study of alloys by the microscope is a 
field which has hardly as yet been entered 
upon, but it promises very valuable re- 
sults. 
A NEw method for producing artificial 
diamonds is described by Dr. Q. Majorana 
in the Rendiconti of the Roman Academy. 
Carbon, heated in the electric are is sub- 
mitted toa pressure of 5,000 atmospheres 
generated by the action of an explosive 
compound on a small piston. The mass 
formed, which consists chiefly of graphite 
and amorphous carbon, is found to contain 
minute crystals, which show the properties 
of the diamond. It thus appears possible 
to transform amorphous carbon into the 
diamond directly without the medium of a 
solvent, which is used in Moissan’s process. 
Tue manufacture of mosaic gold (sub- 
limed stannic sulfid) by the sublimation of 
tin-amalgam, sal ammoniac and sulfur was 
known to the later alchemists, but the part 
played by the sal ammoniac in the process 
has been a matter of conjecture, though the 
old process is in use to-day. It is often 
possible to obtain the mosaic gold by sub- 
liming the precipitated stannic sulfid with 
sulfur, but unless sal ammoniac is present 
this method often fails. In the Zeitschrift 
fiir angewandte Chemie J. Lagutt clears up 
the reaction by showing that the chlorin of 
the ammonium chlorid forms with the tin 
the volatile tetrachlorid, which is in turn 
decomposed by the sulfur, giving the sub- 
limate of mosaic gold, while the ammonium 
chlorid is re-formed. Ammonium bromid 
SCIENCE. 
[N.S. Vou. VI. No. 150. 
can be substituted for the sal ammoniac, 
but no other ammonium salt. The forma- 
tion of the mosaic gold from the direct sub- 
limation of stannic sulfid and sulfur is ac- 
counted for by the presence of hydro- 
chloric acid in the stannic sulfid. If this 
is thoroughly washed free from hydro- 
chloric acid no mosaic gold is found. 
From the new Davy-Faraday Research 
Laboratory comes a solution of another of 
the problems of the past. In 1841 Grove 
described a class of metallic nitrogen com- . 
pounds to which he gave the name of 
‘nitrogurets.’ These were formed by the 
action of six Grove cells on a concentrated 
solution of ammonium chlorid, with anode 
of zine, cadimum, copper, etc., and kathode 
of platinum. Grove supposed the deposits 
to be compounds of ammonium analogous 
to ammonium amalgam, or of nitrogen and 
the metals. In the Zeitschrift fiir Electro- 
chemie Heinrich Pauli describes a repetition 
of the experiments carried out in the Davy- 
Faraday Laboratory, and shows that with 
zine anode Grove’s zine nitroguret is merely 
metallic zine. With copper anode the de- 
posit is a mixture of cuprous oxid and me- 
tallic copper, and with silver anode, silver 
oxid or silver according to the intensity of 
the current. 
THE proposal of Carnot to determine the 
geological age of a fossil by the relative 
quantity of fluorin and phosphate present 
has been applied, at the request of Dubois, 
the discoverer of the fossil remains of 
Pithecanthropus erectus, to determine whether 
this interesting specimen is really Plio- 
cene. J. M. Van Bemmelen gives an 
account, in the Zeitschrift fiir anorganische 
Chemie, of an examination of the remains of 
a fossil elephant found in the same stratum 
with the Pithecanthropus. He finds the 
ratio of fluorin to phosphate in comparison 
with that of apatite to be 0.53, which is 
very close to 0.58, that given by Carnot as 
