_Soluble in Hydrochloric Acid_.
I. II.
Virgin Soil.
Organic matter 4.590 8.5?8
Oxide of iron and alumina 8.939 7.179
Magnesia 0.469 0.677
Lime trace. 0.131
Potash 0.138 0.187
Soda 0.136 0.337
Phosphoric acid 0.100 0.108
Sulphuric acid 0.025 0.117
Silica ---- 0.005
-------- ---------
14.397 17.249
_Soluble in Sulphuric Acid_.
Alumina 17.460 15.684
Magnesia 0.459 0.446
Lime 0.286 trace.
Potash 0.616 1.250
Soda 0.317 0.285
--------- ---------
19.138 17.665
_Residue_.
Silica, soluble 11.675 \
69.546
" insoluble 49.477 /
Alumina 3.062 4.178
Lime 0.700 0.134
Magnesia 0.212 trace.
Potash 0.276 1.180
Soda 0.503 1.048
-------- ---------
100.000 100.000
These are alluvial soils from the Delta of the Irrawaddy.
DRY AIR REFRIGERATING MACHINE.
A large number of scientific and other gentlemen interested in mechanical refrigeration lately visited the works of Messrs. J. & E. Hall, of Dartford, to inspect the working of one of their improved horizontal dry air refrigerators!
The machine, which is illustrated below, is designed to deliver about 10,000 cubic feet of cold air per hour, when running at the rate of 100 revolutions per minute, and is capable of reducing the temperature of the air from 90 deg. above, to about 50 deg. below zero, Fah., with an initial temperature of cooling water of 90 deg. to 95 deg. Fah. It can, however, be run at as high a speed as 140 revolutions per minute. The air is compressed in a water-jacketed, double-acting compression cylinder, to about 55 lb. per square inch --more or less according to the temperature of the cooling water--the inlet valve being worked from a cam on the crank shaft, to insure a full cylinder of air at each stroke, and the outlet valves being self acting, specially constructed to avoid noise in working and breakages, which have given rise to so much annoyance in other cold air machines. The compressed air, still at a high temperature, is then passed through a series of tubular coolers, where it parts with a great deal of its heat, and is reduced to within 4 deg. or 5 deg. of the initial temperature of the cooling water. Here also a considerable portion of the moisture, which, when fresh air is being used, must of necessity enter the compression cylinder, is condensed and deposited as water.
COMPRESSION CYLINDER. SCALE 1/60
After being cooled, the compressed air is then admitted to the expansion cylinder, but as it still contains a large quantity of water in solution, which, if expansion was carried immediately to atmospheric pressure, would, from the extreme cold, be converted into snow and ice, with a positive certainty of causing great trouble in the valves and passages. It is got rid of by a process invented by Mr. Lightfoot, which is at the same time extremely simple and beautiful in action, and efficient. Instead of reducing the compressed air at once to atmospheric pressure, it is at first only partially expanded to such an extent that the temperature is lowered to about 35 deg. to 40 deg. Fah., with the result that very nearly the whole of the contained aqueous vapor is condensed into water. The partially expanded air which now contains the water as a thick mist is then admitted into a vessel containing a number of grids, through which it passes, parting all the while with its moisture, which gradually collects at the bottom and is blown off. The surface area of the grids is so arranged that by the time the air has passed through them it is quite free from moisture, with the exception of the very trifling amount which it can hold in solution at about 35 deg. Fah., and 30 lb. pressure. The expansion is then continued to atmospheric pressure and the cooled air containing only a trace of snow is then discharged ready for use into a meat chamber or elsewhere. In small machines the double expansion is carried out in one cylinder containing a piston with a trunk, the annulus forming the first expansion and the whole piston area the second, but in larger machines two cylinders of different sizes are used, just as in an ordinary compound engine. To compensate for the varying temperature of the cooling water the cut-off valve to the first or primary expansion is made adjustable; and this can either be regulated as occasion requires by hand, or else automatically. The temperature in the depositors being kept constant under all variations in cooling water, there is the same abstraction of moisture in the tropics as in colder climates, and the cold air finally discharged from the machine is also kept at a uniform temperature.