Minerals of high Specific Gravity. 447 
one-third natural size, in the accompanying figure. The glass 
tube 6, about 20° long by 2°2™ internal diameter, is narrowed 
below and fitted with well ground joints to 
the cap e¢ and the hollow stopper a, and 
these parts fit loosely within a large test tube 
d. For holding and heating the apparatus 
the author has found it convenient to make 
use of a metal test-tube stand, made so as to 
fit inside of a tall beaker filled with hot 
water. 
When a separation is to be made it is best 
to previously melt the double salt in a dish 
or casserole on the water bath until it be- 
comes perfectly clear and to dilute it with 
water until it is approximately of the spe- 
cific gravity of the minerals to be separated, 
when, the stopper @ being removed, the 
liquid is poured into the warm separating 
apparatus until the tube 6 is about one-half 
full. The mineral powder is next added, 
and thoroughly mixed, which may readily 
be accomplished by blowing a stream of air 
into the liquid through a small glass tube, 
and then successive portions of water are 
added until the desired separations are 
effected. To obtain the heavy material in ¢ 
the stopper a, previously warmed, is inserted, 
when ¢ can be removed and washed out 
with bot water. By replacing ¢, withdraw- 
ing @ and adding more water another portion can be thrown 
down and separations made almost as quickly and easily as with 
the ordinary stop-cock separating funnels. When one has had 
a little experience in using the Retgers liquid and the appa- 
ratus, almost the only disadvantage that will be found is that 
specitie gravities cannot be taken with the Westphal balance, 
while the decided increase in specific gravity over the other 
heavy liquids makes it exceedingly useful. When it is neces- 
sary to work with large quantities and to throw down a con- 
siderable quantity of some heavy material, it is best to have 
a second apparatus with a larger lower reservoir, c’, fig. 1, but 
it will be found that this is not so convenient for ordinary use 
as one where ¢ is small. 
In aseparation which the author undertook of some monazite 
sand, it was found that the Retgers double salt was not quite 
heavy enough to float some zircon and chromite crystals, and 
an attempt was made to obtain a higher specific gravity by 
varying the proportion of silver and thallium nitrates. Accord- 
1, 
FEE 
[2A AZIZ IZED 
2) 
SSS AES ESS AS Ee OO Oe Se ee Oe ee ee ee eee eee ema weeesesusu=usssuny 
So 
LIZZ IL hah pL 
GZ LLL LLL CLLR MN LL. 
TL 
TSS 
LiL 
(EM 
YZ 
LY 
OY SSSSSSSSSSS 
