990 MINERALS YEARBOOK, 1941

 Because of the complex nature of many coke byproducts, which require special
technical processes, equipment, and operating technique for their economical
production, most byproduct coke plants do not have the necessary facilities
for complete processing of the byproducts and are concerned only with the
major byproducts—gas, tar, light oil and its derivatives, and ammonia
(table 46).
 The total output of coke byproducts reached an all-time high in 1941, although
the total value was slightly less than in 1929 due to the lower selling prices
of ammonium sulfate and light-oil derivatives. In 1941 the total sales value
of all coke byproducts exceeded that of
1940 by $13,727,307 and totaled $158,809,184. This figure represented 50
percent of the value of the coke produced in byproduct ovens. From these
figures it can readily be seen why the byproduct ovens have largely replaced
the beehive ovens in the coke industry (see also fig. 2). Of interest is
the increased output and value of distillate creosote oil. Production in
1941 totaled 38,283,662 gallons compared with 27,150,656 gallons in 1940,
an increase of 41 percent. Sales of distillate creosote oil rose from 62
percent of the total production in 1940 to 102 percent in 1941, thereby increasing
the value of sales from $1,832,348 to $4,583,327. Tar-acid oil, another tar
derivative, is also worthy of mention. The major use of creosote is in wood
preservation, and tar-acid oils are used in the manufacture of plastics,
disinfectants, and dips and for ore flotation.
 Gas.—As gas is now the most valuable coke-oven byproduct, it is given
special attention. in the following tables. Tables 47 and 48 present details
of the quantities recovered, used, and sold in 1941, by States. In addition
to supplying the fuel needs of the coke ovens, a surplus of 554,126,449 .M
cubic feet (62 percent of the total of 892,819,811 M cubic feet of gas produced)
was sold or used for indus-. trial purposes and for distribution through
city mains. Receipts from gas sold by byproduct-coke plants in 1941 totaled
$85,040,609, an advance of $3,638,562 over the 1940 figure of $81,402,047.
The average unit price for 1941, as reported by the operators, was $0.153
per M cubic feet, a decrease of $0.002 per M cubic feet from the 1940 price
of $0.155. The sale of surplus gas produced approximately 53 percent of the
total revenue derived from all the byproducts in 1941.
 Tar.—Tar, a very important coke byproduct, is the basic material for
hundreds of chemical compounds. The crude tar recovered requires special
equipment for complete processing, and many plants that are not equipped
to process the tar sell their crude tar to refineries. Statistics on the
topping of coal tar were collected by the Bureau of Mines for the first time
in 1940, when 94,890,278 gallons were topped. The tar topped in 1941 totaled
103,653,501 gallons. Topping is practiced to obtain from tar at byproduct
plants, where complete refining equipment is not available, certain constituents,
including light oil and tar acid fractions, and in some plants, even higher
fractions. Growing recognition of the importance of creosote oil, a derivative
of coal tar, is indicated by the increase in its production and value in
1941. The wasteful practice of burning tar for fuel is steadily being discontinued,
and the recovery of its valuable constituents is being practiced by more
plants each year. Statistics on the production and sales of coke-oven tar
during 1941 are shown in table 49.
 Ammonia.—Another major byproduct of the coke ovens is ammonia. It
is used in the manufacture of nitric acid, explosives, and commer