448 Penfield—Devices for the Separation of Minerals, ete. 
ingly prepar ations were made having the following proportions : 
AgNO,: TINO, = 3:4, 2:4 and 1:4, and separations with 
these were made in test tubes. The 3:4 preparation fused 
below 100° C. and on it most of the zircon and some of the 
chromite floated, the specific gravity of the separated product 
being 4°678. The 2:4 preparation was fused in an air bath* 
heated to 150° C. and on it the remainder of the zireon and 
some chromite floated, sp. gr. 4°78. The 1:4 preparation was 
fused at about 200° C. and on it some chromite floated, sp. gr. 
4°85. Lastly thallium nitrate was used, when the temperature 
of the air bath had to be about 250° C. and a final product of 
chromite was separated having asp. gr. of 4:94, while only a 
few dark grains were left with ‘the monazite. Thus in eases of 
emergency a supply of the above mentioned preparations, 
enough to make from 5 to 10° of fused material, may be 
found convenient. 
An attempt was made to separate chalcopyrite, sp. gr. = 4°2, 
from linneite, sp. gr. = 4°85, but it was found that the min- 
erals were attacked by the Retgers liquid. Pyrite is also 
attacked, and it is evident that it is not safe to apply this 
method to the separation of sulphides, althongh it may answer 
in some cases. 
In taking the specific gravity of separated mineral fragments 
the author believes that in many cases the following method 
will be found more convenient and simpler than the 
pycnometer. The fragments, boiled in water to expel 
air, are transferred to a tube with a loop of platinum 
wire fused into the glass for a handle, shown in natural 
size in fig. 2, and when suspended by a fine platinum 
wire the weight in water can be taken on a chemical 
balance. The powder is then transferred to a watch 
glass by means of a jet of water and its weight ascer- 
tained after drying, while the tube is weighed empty in 
water. The narrow tube is more favorable for weigh- 
ing in water than a pan would be, as it offers less resist- 
ance to the swinging of the balance. 
Separating apparatus according to the author’s draw- 
ings have been made by the firms Alvergniat Freres, 
10 Rue de la Sorbonne, Paris, and by Messrs. Eimer 
and Amend of New York. 
Laboratory of Mineralogy and Petrography, 
Sheffield Scientific School, New Haven, October, 1895. 
* One described by J. H. Pratt and the author is a convenient form to use. This 
Journal, III, xlvii, p. 83, 1894. 
