434 MINERALS YEARBOOK

petroleum and 1 part of coal, ground through 200 mesh and stabilized by the
addition of 1 or more percent of certain chemicals such as limerosin soaps,
coal-tar fractions, etc.4 The evaporative capacity, the efficiency of steam
generation, and the performance of the vessel at sea were excellent and almost
equaled that of oil alone. It was claimed that the coal would not separate
from the oil to any material degree in a 6-month period. With modern equipment,
grinding in a colloid mill may decrease the need of adding stabilizing chemicals.
However, such very fine grinding is costly and would eliminate the relatively
small margin that now exists between the cost of coal and oil for bunker
use.5
 Goal-di.tst engine.—Work is being continued in Germany. on overcoming
the difficulties of using coal dust as diesel-engine fuel. Wantzel,6 studying
the influence of air excess, air temperature, injection pressure, particle
size, and composition of coal on the ignition, temperature, ignition lag,
and ignition limit, found that ignition lag depended principally on the size
of the finest coal particles. If no very fine particles were present in a
dust the ignition lag increased rapidly. Pawlikowski7 hopes to eliminate
the abrasive action of fused ash particles by leaching the pulverized co.al
with dilute mineral acids to remove fusible ash-forming constitutents.

BROWN COAL AS FERTILIZER

 The direct application of pulverized coal as a fertilizer was tried by Lampadius8
at Freiberg in the beginning of the nineteenth century. Recently, German
investigators have found that agricultural yields from soil lacking humic
compounds were improved by direct application to the soil of limited amounts
of raw, pulverized brown coal; better results were obtained by treating the
coal with ammonia or nitric acid and ammonia to form soluble humates.8 9
10 11 The favorable action of these coal humates is due partly to improving
the physical, chemical, and biological condition of the soil (thus promoting
better utilization of plant foods)89 1011 and possibly to furnishing part
of the plants' carbon requirements.'2
 Nemac,~ of the Prague Agricultural Experiment Station, concludes that while
brown-coal preparations improve the physical condition of poor soils, such
improvements occur slowly, and observations over a number of years will be
required to obtain reliable information. Although American lignites represent
a more advanced stage of coal formation than the German brown coal they may
serve as raw materials for humic preparations.
 4Sheppard, S. E., Colloidal Fuels, Their Preparation and Properties. md.
and Eng. Chem., vol. 13,1921, pp. 37—47.
 ' Brame, J. 5.5., Colloidal or Coal-Oil Fuel. Jour. Soc. Chem. md., (London),
vol. 51,1932, p. 8.55.
 6 Wantzel, W., The ignition and combustion process in the coal dust engine.
Fuel (London), vol. 11,
1932, pp. 177—196,222—228.
 Pawlikowski, Rudolf, Improvements In Preparatory Treatment of Pulverized
Fuel for Engines and Furnaces: British Patent 370461, Apr. 4, 1932.
 8 Eck, L., Investigation of the Fertilizing Action of Bituminous Coal. Ztschr.
angew. Chem., vol. 45,
1932, p. 124.
 8 Kissel, A., The Use of Coal as a Fertilizer. Trans. Fuel Conference, World
Power Cong., London, 1928, vol.1, pp. 80—101.
 10 Kissel, A., The Use of Low-Grade Brown Coals as Raw Material for the
Preparation of Fertilizers. Brennstoff-Chem., vol. 13,1932, p. 414.
 11 Lieske, R., Investigations on the Use of Coal as Fertilizer. Brennstoff-Chem.,
vol. 12, 1931, pp. 81,
426—434.
 12Geiter, I., The Possibility of Making Brown Coal Available for Plant Food.
Braun Kohlen Archly., vol.36, 1932. pp. 43—55.
 ' 3Nemac, A., The Use of Brown-Coal Preparations as Fertilizers. Brennstoff-Chem.,
vol. 13, 1932, p. 168.