DHOSHJATE ROCE
05

to the flotation plant for recovery. At the drying plant the railroadtrestle
type of stock piling is used for the wet rock, with a tunnel belt-conveyor
system for recovery and transportation to two large electrically driven,
oil-fire, rotary-kiln driers. The dried rock is stored m loading bins pending
shipment or pulverized and delivered direct to railroad cars. The dust from
the driers is collected in enclosed bins in the storage and loading building.
 The utilization of Hardinge conical scrubbers for the reduction of clay
balls and the release of clean phosphate rock from the clay matrix in land-pebble
phosphate-rock washers is described by J. K. Towers.3
 The flotation of phosphate rock is discussed in two recent papers by C.
E. Heinrichs ~ and H. S. Martin.5 The first of these papers emphasizes the
importance of flotation in the economics and technology of the phosphate-rock
industry, referring to the benefits obtained by its use, such as greater
flexibility in grade of product, decreased over-all production costs, increased
recoveries, doubling of available reserves, and reduction of capital investment
for a given producing capacity; it also presents data to ifiustrate some
of these points. Flotation, by reclaiming the valuable part of the fines
formerly run to waste, is said to practically double the recovery of phosphate
rock. The second paper describes the operations and costs at the no. 2 flotation
plant of the Phosphate Recovery Corporation near Mulberry, Fla.
 A detailed description by N. K. Karchmer 6 of the flotation of apatite in
Russia has current domestic interest because of an investigation by the United
States Tariff Commission (referred to under the section on imports). The
apatite-bearing nephelinc-syenites mines are in the western part of the Kola
Peninsula in northwestern arctic Russia. The flotation plant is about 4 miles
from the mine. The principal crushing of the apatite rock is followed by
two-stage grinding, conditioning of the flotation feed, roughing and cleaning,
thickening, filtering, and drying. Oleic acid and peat tar are used as flotation
agents. A detailed flow sheet of the flotation plant accompanies the description.
 Comprehensive papers by B. G. Klugh ~ and W. H. Waggaman,8 published during
the year, discuss in considerable detail the production of phosphoric acid
from phosphate rock by the volatilization or furnace process.
FOREIGN TRADE

 Export$.—The downward trend in both quantity and value of exports,
which began in 1931, continued in 1932 at an increased rate. All groups participated
in the dedlin~. Land-pebble (and other) phosphate-rock exports fell from
846,012 long tons valued at $3,663,113 in 1931 to 547,026 long tons valued
at $2,390,122 m 1932. Ex' Towers, J. K., Improvements in Mineral Scrubbing:
Eng. and 1,~in. Jour., vol. 133, no.3, March 1932,
p. 174.
 ' Heinrichs, C. E., Phosphate Flotation, Its Place in the Technology and
Economics of the Phosphate Industry: Paper read at the New York meeting,
February 1933, of the American Institute of Miiung and Metallurgical Engineers.
 ' Martin, H. S., Milling Methods and Costs at the No.2 Concentrator of the
Phosphate Recovery Cor. poration: Paper read at the New York meeting, February
1933, of the American Institute of Mining and Metallurgical Engineers.
 Karchmer, N. K., Flotation of Apatite in Russia: Eng. and Mi Jour., vol.
133, no. 8, August 1932, pp. 429-432.
 7KIugh, B. G., Thermal Production of Phosphoric Acid: md. and Eng. Chem.,
vol. 24, no. 4, April
1932 pp. 371—374.
' Waggaman, W. H., Present Status and Future Possibilities of Volatilization
Process for Phosphoric Acid Production: md. and Eng. Chem., vol. 24, no.9,
September 1932, pp. 983-988.