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Vegetable, Animal, and Essential Oils Vegetable oil exports gained 30 per cent, shipments being 114,261,000 pounds valued at $12,579,000, as cofipared with 88,590,000 pounds valued at $9,474,000. This gain was largely due to greater shipments of cottonseed oil, of which Canada took half the total of 62,415,000 pounds. Coconut oil exports were 17,901,000 pounds valued at $1,764,000, about the same as in 1924. Imports of vegetable oils, expressed, and fats were valued at $74,988,000 as against $59,667,000 in 1924. They were chiefly Chinese wood oil, 101,554,000 pounds valued a t $11,386,000, a8 compared with 81,588,000 pounds valued at $11,092,000 in 1924; coconut oil, 233,174,000 pounds valued a t $19,726,000, compared with 224,763,000 pounds valued a t $17,301,000 in 1924; edible olive oil, 90,426,000 pounds valued at $15,656,000 as compared with 76,186,000 pounds valued a t $12,585,000, in 1924; and palm oil, 139,179,000 pounds valued a t $11,040,000, compared with 101,780,000 pounds valued a t $7,002,000 in 1924. Flaxseed imports were 16,510,000 bushels valued at $39,683,000 as compared with 16,589,000 bushels valued a t $30,038,000 in 1924. Imports from Canada, 5,917,000 bushels valued a t $14,382,000, compared with 2,750,000 bushels valued a t $6,030,000 in 1924, and those from Argentina, 10,537,000 bushels valued at $25,167,000, compared with 13,838,000 bushels valued a t $24,005,000. Exports of animal and fish oils, fats, and greases fell from 1,225,000,000 pounds to 942,000,000 pounds, chiefly because of lower lard shipments, especially in the trade with Germany. In essential and distilled oils exports of oil of peppermint, 68,000 pounds, were less than half the 1924 total. Of the imports of essential and distilled oils, valued at $6,345,000 last year, citronella and lemon-grass oil formed the largest single item with 1,322,000 pounds valued at $1,059,000. Ceylon and the Dutch East Indies furnished the bulk of the imports of citronella oil. Dyeing and Tanning Materials Imports, valued at $8,190,000, were 33 per cent higher than in 1924. Quebracho extract, 113,177,000 pounds (92,544,000 pounds in 1924) was valued a t $3,946,000 ($2,584,000 in 1924), the average import valuation rising from 28 cents in 1924 to 35 cents in 1925. Exports of chestnut extract, 7,287,000 pounds valued a t $217,000, were 20 per cent less. Logwood extracts for dyeing, 2,225,000 pounds, gained 50 per cent over 1924. Rubber
Because of its spectacular price rise, rubber furnished the great sensation of the year. Pricea reached their peak in July, and since then have fluctuated widely but have maintained an average much higher than for many years past. Imports, however, were far higher than ever before, totaling 888,478,000 pounds valued a t $429,705,000, as against 734,845,000 pounds valued a t $174,231,000 in 1924. In 1925 the British East Indies sent us 587,537,000 pounds, the United Kingdom 84,259,000 pounds, the Dutch East Indies 153,241,000 pounds, and Brazil 34,715,000 pounds. I n 1924 these countries furnished the following: British East Indies, 472,625,000 pounds, the United Kingdom 85,237,000 pounds, the Dutch East Indies 131,763,000 pounds, and Brazil 29,026,000 pounds. Imports of guayule, a Mexican product, increased from 3,038,000 pounds to 8,469,000 pounds, and of scrap and reclaimed rubber from 12,168,000 pounde to 25,459,000 pounds. Naval Stores, Gums, and Resins Imports of gums, resins, and balsams were $30,751,000 as against $28,763,000 in 1924. Of the varnish gums and
Vol. 18, No. 3
resins shellac with 19,912,000 pounds valued at $10,164,000, as compared with 24,553,000 pounds valued at $13,139,000 in 1924, was the most important. Crude camphor imports were nearly a third greater, 2,369,000 pounds as compared with 1,848,000 pounds. Synthetic camphor totaled 1,835,000 pounds valued a t $921,000 and refined natural camphor 1,584,000 pounds valued a t $953,000. The average value of the synthetic was thus about 50 cents and that of the refined natural 60 cents. Chicle imports picked up by 50 per cent-12,145,000 pounds against 7,919,000 pounds in 1924. Gum arabic, 7,256,000 pounds valued at $783,000, and gum tragacanth, 966,000 pounds valued a t $428,000, were much the same as in 1924. Tn the export trade in rosin, large quantities went to twelve or fifteen countries, the United Kingdom leading with 22 per cent, Germany taking 21 per cent, and South America 19 per cent. Total exports were 1,172,000 barrels, a drop of 20 per cent from 1924, but the value, $18,888,000, was 40 per cent greatey. The average declared value was thus much higher, $16.11 per barrel as compared with $9.40 in 1924. Spirits of turpentine also showed a small increase, from 11,510,000gallons valued at $10,105,000 in 1924 t o 11,557,000 gallons valued at $11,346,000 in 1925. The United Kingdom took about 60 per cent last year. The average export valuation rose from 88 cents to 98 cents per gallon.
A Mobile Refrigerating Unit' By H. F. Pierce DEPARTMENT OF PHYSIOLOGY, COLUMBIA UNIVERSITY, New YORK, N. Y.
H E advent of the small, electrically *operated refrigerating plant, designed primarily for use in the home, has provided hospitals and laboratories with a convenient means of chilling perishable materials, and of maintaining conditions of low temperature either for storage or for the performance of certain types of experiments. Such a refrigerating unit consists essentially of a motordriven compressor pump, a cooling coil, an expansion valve, and an expansion coil located in a brine tank. The thermostatic control provided consists of a metal bellows (sylphon tube2) containing a volatile liquid which by its expansion and contraction actuates the starting switch of the compressor motor. When the brine temperature falls the motor stops; when it rises the motor starts again, thus making the unit automatic in operation. The brine tank is designed to occupy the ice compartment of the usual household refrigerator. In order to extend its field of usefulness, Prof. Ernest L. Scott, of this department, conceived the idea of mounting the refrigerating unit on a low truck so that it might be easily moved about the laboratory; of placing on the same base a cooling chamber in which materials could be stored and certain experiments performed; and of connecting to the brine tank a motor-driven pump which should serve the double purpose of keeping the cold brine in circulation through the unit and of pumping it through any outside apparatus in which it might be desirable to maintain a low temperature. The work of constructing this mobile unit was begun under the direction of Professor Scott and completed by the author. Figure 1 shows the apparatus and the disposition of its various parts. The brine tank, C, is insulated on the sides and bottom with 4 inches of sheet cork and on the top with 6 inches of granulated cork, and the whole is inclosed in a wooden casing which serves to protect the insulation and to support the relays, switches, and other control devices.
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Received October 15, 1925. Awbery, J . Sci. Instruments, 8 , No. 11, 358 (1925).
* Criffiths and
March, 1926
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for the remote control of motors, heating devices, or large groups of lamps, and is so designed that in closing it completes two circuits, one supplying the motor or other device, the other maintaining the flow of current through the relay and keeping it closed until its coil is short-circuited by some outside connection. This relay w d l safely break a current of 15 amperes a t a pressure of 125 volts, and requires only 0.027 ampere for its operation. The telegraph relay was modified by the addition of a second insulated contact, so that the armature makes an electrical connection a t each end of its stroke. When the temperature of the brine rises, the mercury mounts in the capillary tube and touches the nickel wire, the telegraph relay closes, the contactor relay closes, and current flows to the motor. When the operation of the unit has reduced the brine temperature so that the mercury falls, the telegraph relay opens and makes a second contact. This shortcircuits the contactor relay coil through the resistance R, the contactor relay opens, and the motor stops. Owing to vibration caused by the motors and pumps and consequent repeated momentary contacts a t the mercury surface, the light armature of the telegraph relay had a tendency to flutter back and forth between its contacts. This tendency was overcome by attaching to the armature a short rod carrying a ball which fits closely in a cylindrical brass cup filled with heavy oil (T,Figure 2). Thus damped, the relay requires approximately 30 seconds to close and an equal length of time to open. Hence, in spite of vibration a t the mercury surface, there is no chattering of either relay, and the motor starts and stops smoothly. Damping the relay naturally interferes somewhat with the sensitivity of the control, but it is necessary because of the Figure 1-Mobile Refrigerating U n i t A , compressor pump, B , cooling coil, C, brine tank; D, brine circuwear and tear which would otherwise accrue with more lating pump, E , cooling chamber; F and G, outlet and inlet for cold frequent starting and stopping of the motor. brine supplied to outside apparatus; H, controlling valvf s; J mercury thermostat, K,resistance shunted across mercury contart; i,damped The accuracy of the thermostatic control is very good, telegraph relay, M ,contactor relay; N , plug for attaching unit to electric mains considering the fact that the temperature is regulated by controlling the compressor motor. -4Beckmann thermomSince the sulfur dioxide thermostat supplied with the unit eter placed (in air) in the cooling chamber showed a deallowed a variation in brine temperature of some 10' C., viation from the mean of *0.075' C. over a period of 4 hours it was decided to build a more sensitive control device. a t a temperature of approximately 0" C., with a room temProf. H. B. Williams, of this department, suggested the use perature varying between 17" and 22' C. With marked of a large mercury thermostat, the mercury to be contained changes in room temperature a somewhat larger deviation in a steel tube and the usual glass capillary tube to be at- has been observed, but in all cases the temperature has retached to it by means of a perforated rubber stopper. This mained within =!=0.25' C. over periods ranging from 1 day suggestion was adopted, and the mercury thermostat, used in to 2 weeks. connection with the control system devised by the author, has given entire satisfaction. The steel tube is 14 inches 4 1 I long and 0.5 inch in internal diameter, and is plated with tin outside to prevent corrosion. During the process of filling, the mercury was boiled in the tube to eliminate air bubbles. The tube is provided with a threaded brass head which makes a tight joint with an opening in the top of the brine tank, and to this head is attached a brass tube which is concentric with and furnishes support and protection I I for the glass tube piercing the rubber stopper. Kear the upper end of the glass tube is a %way cock, which allows MOTOR the thermostat tube to be connected with the mercury reserFigure 2-Thermostatic Control Apparatus voir. Attached to the upper end of the brass tube but insulated electrically from it is an arm carrying the nickel wire I n place of the usual calcium chloride brine we are using which makes contact, with the mercury in the capillary tube. a 35 per cent alcohol-water mixture. This fluid is satisThe mercury thermostat is connected through three factory for temperatures as low as -15' C., and it has a standard dry cells with a telegraph relay, L. In order t o refrigerating capacity nearly equal to that of a 25 per cent minimize sparking at the surface of the mercury, a high re- calcium chloride s ~ l u t i o n . ~ It has the advantage of being sistance, K , is shunted across the gap. A "variable grid- noncorrosive to the metal parts of the system and of leaving leak," 0 to 50,000 ohms, as used in radio receh-ing apparatus, no hygroscopic deposit in case any is spilt. serves admirably for this purpose. This apparatus has been in nearly constant use during Since the motor requires a larger amount of ,current than the greater part of a year, and has required little attention can be carried safely by the telegraph relay, a contactor other than cleaning and oiling. relay, M , is employed This is a commercial deT.ice intended 8 Zoller, THIS JOURNAL, 16, 1073 (1924).
The rotary pump, D,which circulates the cold brine through the cooling chamber, E, and any outside apparatus attached to F and G, is, with the regulating valves, housed in a metal box filled with granulated cork. The cooling chamber is an annular copper tank covered with compressed cork insulation. It rests on a sheet cork base and is provided with a movable cover of the same material. Its depth is 14 inches, its diameter 10 inches. A small fan in the chamber keeps the air in circulation and assists in maintaining an even temperature.
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