I X D USTRlAL AND ENGINEERING CHEJIISTRY
March, 1926
267
Our Foreign Trade in Chemicals in 1925’>’ By Otto Wilson hf1,sSEY
BUILDISG,WASHINCTOX, D. C.
UBSTANTIAL gains, both in imports and exports, featured our 1925 foreign trade in chemicals and chemical products. Imports increased more than exports, largely because of heavier trade in “chemical products.” I n the trade in pure chemicals the strong lead of exports over imports was only slightly reduced.
S
Foreign Trade of the IJnited States In Chemicals and Allied Products Year Imports Exports Balance of trade $ 50,934,000 $ 37,037,000 Average 1909-14a $ 87,971,000 524,868,000 +414,652,000 Average 1915-19a 110,216,000 176,733,000 $. 58 449 000 Average 1919-23 118,284,000 10:208:000 121,726,000 111,518,000 1924 15,931,000 140.386.000 124,455,000 1925 a Fiscal y e a n
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A s compared with the pre-war trade the increased value of imports corresponds with the general price increase. But in the export trade there has evidently been a marked gain in volume as well as values. Outstanding features of the 1925 import trade were a notable falling off in coal-tar crudes, and about an equal gain in finished products; and gains in medicinals, paints, pigments, and varnishes, and fertilizers. I n the export trade coal-tar crudes also decreased and finished products gained. Aledieinals, chiefly patent medicines, showed a big increase. Exports of pigments, paints, and varnishes were larger than in 1924 by some 30 per cent. Sulfate of ammonia exports remained about the same but phosphate rock showed a healthy gain. Explosives, soaps, pyroxylin products dentifrices, etc., were sold abroad in considerably greater quantities than in 1924. . The following table shows the trade by sub-groups in the last two years: U. S. Trade in Chemicals and Allied Produrts ----Exports--Imports-1924 1925 1924 1925 Chemicals $53,434,735 $38,277,283 $43,122,533 $48,896,441 Pigments, paints, and varnishes 14,326,600 18,511,010 2,822,702 3,235,210 Fertilizer and materials 16,508,398 17,298,529 66,531,495 78,071,966 Euploswes, ammunition and fireworks T,415,619 8,419,399 957,911 1,103,826 Niscellaneous 19,833,228 21,948,524 8,291,126 9,078,447
Chemicals and Allied Products Chemicals
COAL-TIR PRODTJ(’TS-h coal-tar products trade showed a fair increase in both directions in 1925, imports being larger by 8 per cent and exports by 3 per cent. Trade of Last Two Years in Coal-Tar Products --Exports-Imports-1924 1925 1924 1925 Crudes $3,270,000 $ 2,716,000 $14,366,000 $12,026,000 Intermediates 363,000 471,000 807,000 1,098,000 Finished products 6,343,000 7,574,000 4,946,000 7.533.000
TOTAL
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--
$9,976,000 810,761,000 $20,110,000 $20,657,000
Two notable features of the import trade were a drop of 5 per cent in dead or creosote oil, from 89,688,000 gallons in 1924 to 84,869,000 gallons in 1925, and a gain of 68 per cent in colors, dyes, and stains, from 3,434,000 pounds to 5,782,000 I
8
Received February 12, 1926. All 1925 figures are preliminary
pounds, The creosote oil decrease was due to a sharp decline of 40 per cent in shipments from the United Kingdom, the chief source of supply. I n 1924 that country sent us 59,595,000 gallons and in 1925, 35,550,000 gallons. The deficit was largely made up by greater imports from the Netherlands, which grew from 10,325,000 gallons to 30,325,000. The gain in imports of coal-tar colors and dyes was due chiefly to greater shipments from Germany-2,932,000 pounds valued a t $3,768,000. The 1924 amount was 1,633,000 pounds valued at $2,079,000. Exports of coal-tar colors, dyes, and stains showed a marked advance, from 15,713,000 pounds in 1924 to 25,800,000 pounds in 1925. But average export values were nearly a third lower, so the total value increased only from $5,635,000 to $6,694,000. The grade of these exports as compared with imports is indicated by the fact that their average declared value is only one-fourth to one-fifth of that of the imports from Germany. China continues to be the great market for these goods, increasing her share of the exports from 60 per cent in 1924 t o 70 per cent in 1925. Japan took about 8 per cent last year as compared with 20 per cent the year before. )lEDICIKA4LS AXD PHARMZ4CEUTICALS-EXpOrtS under this heading rose from $17,441,000 in 1924 to $19,768,000 in 1925, and imports from $4,777,000 to $5,832,000. Exports consist largely of proprietary medicines. England is much the biggest buyer, taking $3,324,000 out of a total of $17,637,000 last year. Cuba took $2,503,000 worth, and Mexico, Canada, South America, and British India were important buyers. Antitoxins, serums, and vaccines exports totaled $1,249,000 as compared with $1,058,000 in 1924, with imports negligible. Exports go largely to Latin tropical and subtropical countries, Cuba and Spain leading with about 18 per cent each. Under the head of medicinals our chief import is menthol, 294,000 pounds as against 193,000 pounds in 1924. Japan sent us 270,000 pounds in 1925. England, France, Canada, and Germany sent us a few thousand pounds each. Imports of quinine sulfate and other cinchona salts were six times as heavy as exports last year, the former being valued a t $1,322,000 and the latter a t $237,000. Imports were somewhat smaller in quantity than in 1924, but exports were more than twice as large. The Netherlands and Japan mere the two chief sources of supply, as usual, but the former country sent us only 1,887,000 ounces as against 2,322,000 in 1924, while Japan increased her trade from 474,000 ounces to 540,000 ounces. ACIDSAND A N H Y D R I D E S -one ~ ~ substance ~ under this head figured in the trade last year to the extent of more than $1,000,000; that was arsenious acid, or white arsenic, of which we imported 18,631,000 pounds valued a t $1,076,000. The total value was a third less than the 1924 figure, 81,591,000, although the quantity increased 8 per cent. Shipments from Mexico, the chief source of supply, showed a big gain, amounting to 10,113,000 pounds as compared with 3,800,000 pounds in 1924. Sulfuric acid exports decreased a third, while imports more than doubled. The trade is almost entirely American, Mexico and Cuba being the leading buyers and Canada practically the sole source of foreign supply. Exports were 7,537,000 pounds valued a t $152,000 in 1925 and 11,273,000 pounds valued a t $180,000 in 1924, while imports of 36,383,-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
000 pounds valued a t $242,000 compared with 15,249,000 valued at $13$,000 in 1924. Imports of citric, oxalic, formic, and tartaric acids ranged from $100,000 to $700,000 each. OTHERCHEMICALS-In alcohols the outgoing and incoming trade last year about balanced. The former was valued at $709,000, as compared with $900,000 in 1924, and the latter a t $735,000, against $504,000 in 1924. Foreign sales of methanol, the chief alcohol export, were cut from 641,000 gallons valued at 8687,000 in 1924 to 408,000 gallons valued at $321,000 last year, the average valuation being reduced from $1.07 per gallon to 78 cents. Japan in 1925 displaced England as the largest buyer, taking 105,000 gallons or 26 per cent, as compared with 24 per cent for England, 19 per cent for Cuba, and 15 per cent for Canada. Ammonia and ammonium compounds figure in both the import and the export trade. Imports, divided evenly in 1925 between chlorides and nitrates, grew from 15,476,000 pounds valued at $742,000 in 1924 to 23,893,000 pounds valued at $1,095,000 last year. Exports also increased in quantity but fell o f f in d u e , the figures being 4,521,000 pounds valued at $871,000 in 1925 and 3,496,000 pounds valued at $916,000 in 1924. Sales of aluminium sulfate in 1925, amounting to 41,512,000 pounds valued a t $506,000, were 30 per cent higher in quantity than in 1924. As in 1924 about 90 per cent of the sales went to Canada. I n the trade in soda and sodium compounds this country is largely an exporter. Last year we sold to foreign countries over one-third of a billion pounds of these chemicals, valued at $8,353,000, whereas imports were only about 50,000,000 pounds valued at $3,500,000. While the volume of exports represented about a 12 per cent gain over the previous year, the total value of the trade showed a slight decrease. Much the largest export item was caustic soda, 100,955,000 pounds valued a t $2,996,000, which compared with 92,116,000 pounds valued at $2,863,000 in 1924. The trade was widely scattered but near-by countries were the biggest buyers, except for Japan, whose purchases rose to 22,205,000 pounds as against 10,517,000 pounds in 1924. Of the imports of sodium compounds two-thirds are made up of sodium cyanide, of which we obtained 30,212,000 pounds in 1925 from abroad, valued at $2,600,000, about the same as in 1924. Canada supplied by far the larger part, 24,645,000 pounds, with much smaller amounts coming from Germany and France. Imports of potassium compounds were valued at $4,590,000, a 50 per cent increase over 1924. About a third were argols, 24,666,000 pounds, France sending about half. Spain increased her shipments from 1,641,000 pounds to 4,457,000 pounds, while those from Italy fell from 2,923,000 pounds to 2,098,000 pounds. Calcium carbide imports, 14,240,000 pounds valued a t $515,000, were somewhat less than in 1924. These come almost wholly from Canada. Barium compounds amounting to 20,112,000 pounds, valued at $298,000, were 40 per cent more than in 1924. As in 1924 about four-fifths came from Germany. Glycerol imports advance strongly to 21,300,000 pounds valued at $2,541,000, a 40 per cent gain. France led among the many sources of supply with 6,422,000 pounds, a 70 per cent gain, while England sent us 5,303,000 pounds, a 9 per cent loss. Belgium, Germany, Netherlands, Spain, Canada, Cuba, and Argentina also figured in the trade. Magnesium compounds, 24,347,000 pounds valued a t $212,000, were about the same as in 1924. Benzene exports, largely to England and France, were 58,890,000 pounds in 1925 and 57,882,000 pounds in 1924. Besides those already mentioned, chemicals exported to a
Vol. 18, Xo. 3
value of t1,000,000 or more in 1925 included baking powder, 4,026,000 pounds valued at $1,533,000, sent to all parts of the globe; calcium compounds, 54,281,000 pounds valued at 31,365,000; petroleum jelly, 6,482,000 pounds valued at 51,075,000; and dextrine or British gum, 22,678,000 pounds valued a t $1,031,000. I n all these articles there were no striking trade fluctuations from the previous year. Pigments, Paints, and Varnishes -4s the detailed figures show, this is largely an export trade, our foreign purchases being in the nature of raw materials and our foreign sales manufactured goods. Two Year’s Trade in Pigments, Paints, and Varnishes -Exports-Mineral earth pigments Chemical pigments Paints, stains, and enamels Varnishes
TOTAL
-Imports---
1924
1925
$ 823,000
$ 904,000
5,898,000 5,998,000
1924
1925
$1,083,000 $1,210,000 7,679,000 1,287,000 1,455,000
7,903,000
377,000
519,000
1,607,000 2,025,000 74,000 51.000 -
14,326,000
18,511,000
2,823,000
3,235,000
In the export trade about a third of the total value is represented by ready-mixed and other paints. Enamel exports showed the greatest gain, from 1,875,000 pounds to 2,663,000 pounds. The enamel trade is widely scattered, Canada, England, Mexico, and Argentina taking important quantities. Ready-mixed paints also find buyers all over the world, Cuba and Mexico leading in the 1925 trade with about 30 per cent and 9 per cent, respectively. Bone black, carbon, and lampblack are the chief chemical pigments exported. Carbon black accounted for 43,182,000 pounds valued at $3,556,000 (a large part of this material, however, finds other uses than as pigment). White lead, with exports of 13,663,000 pounds valued a t $1,293,000, and zinc oxide, 21,710,000 pounds valued at $1,503,000, were large items in 1925. Of the former the United Kingdom took 8,349,000 pounds. The United Kingdom’s purchases of zinc oxide increased sevenfold, from 1,388,000 pounds in 1924 to 9,743,000 pounds in 1925. Canada was likewise a bigger buyer, taking 8,640,000 pounds as against 5,123,000 pounds in 1924. These increases accounted for a large part of the almost threefold increase in total exports of zinc oxide in 1925. Oil varnish exports gained 9 per cent, being 712,000 gallons valued at $1,279,000, as against 652,000 gallons valued at $1,123,000 in 1924. The trade is widely scattered, with the United Kingdom leading and Italy and Sweden taking large amounts. I n the import trade in paints, pigments, and varnishes, ochers and siennas and other earth pigments made up 40 per cent of the value and lithopone and other chemical pigments most of the remainder. Nearly all of these two classes of imports came from continental Europe, chiefly France, Belgium, Spain, and the Netherlands. Imports of paints, stains, and enamels were 1,558,000 pounds valued at $519,000, about 50 per cent more than in 1924. Germany supplied 45 per cent and the United Kingdom 20 per cent. Fertilizers and Fertilizer .Materials
Both exports and imports of fertilizers and materials gained in 1925. Exports were 1,147,000 tons valued a t $17,299,000 as compared with 1,068,000 tons valued a t $16,508,000 in 1924; and imports were 2,268,000 tons valued a t $78,072,000 as compared with 1,893,000 tons valued a t $66,531,000. I n last year’s review the statement was made with regard to Chilean nitrate imports that “that (pre-war) average, if the present rate of increase holds, will be almost doubled in
March, 1926
INDUSTRIAL AND ESGINEERING CHEMISTRY
another year.” The prediction is borne out by the 1925 returns, which with those of preceding years were as follows: Chilean Nitrate Imports Tons Value Value Der ton - .__ $17,615,000 $32.26 Average 1910-14a 546,000 46,215,000 39.40 Average1915-194 1,173,000 33,754,000 47.81 706,000 Average 1919-23 47,169,000 47.80 987,000 1924 52,531,000 47.23 1,112,000 1925 Fiscal years.
The average valuation per ton was lower in 1925 than for any other year since the war, except 1923. Among other large import items were 98,000 tons of calcium cyanamide or lime nitrogen, 84 per cent of which came from Canada. Imports of potash fertilizers increased from 632,000 tons valued a t $10,440,000 in 1924 to 821,000 tons valued a t $13,051,000 in 1925. The share of France and Germany in the four chief classes in 1924 and 1925 is shown in the folloiving table: P o t a s h I m p o r t s from F r a n c e a n d G e r m a n y (Tons) Manure salts Chloride, crude Sulfate, crude -Kainite1924 1925 1924 1925 1924 1925 1924 1925 France 4 7 7 5 4 3 4 8 4 5 5 6 5 8 7 7 2 3 8 1 3 2 7 6S9SO 8 4 3 5 7 9 5 2 8 7 Germany 71:808 107:851 66:375 59:191 68:845 108:387 12S:986 259:260
In our export trade in fertilizers, Japan and the Dutch islands Java and Madura took most of the ammonium sulfate, the former 52,000 tons valued a t $2,968,000 (32,000 tons valued a t $1,979,000 in 1924), and the latter 46,000 tons valued a t $2,439,000 (37,000 tons valued a t 82,108,000 in 1924). Total ammonium sulfate exports were 123,000 tons valued a t 56,749,000 as compared with 118,000 tons valued a t $6,919,000 in 1924. Phosphate rock exports, 870,000 tons valued a t 55,678,000 gained 6 per cent over 1924. Land pebbles made up four-fifths of the exports, Spain leading as buyer with 108,000 tons, followed by the Netherlands, Japan, Germany, and Italy. These countries also led in 1924, but in different order, Germany dropping from 129,000 tons in 1924 to 94,000 tons last year and Japan rising from 46,000 tons to 95,000 tons. Total exports of phosphate land pebbles were 698,000 tons valued a t $3,287,000 as compared with 686,000 tons valued a t $3,210,000 in 1924.
269
15 per cent. These goods are very widely distributed, going in considerable quantities to all parts of the world. Exports of talcum and other powders were 3,469,000 pounds valued at $1,882,000, as against 3,229,000 pounds valued at $1,688,000 in 1924. Perfumery and toilet waters were valued a t $451,000 ($410,000 in 1924). Exports of pyroxylin products in sheets, rods, or tubes, amounted to 2,464,000 pounds valued at $2,087,000, as against 2,004,000 pounds valued a t $2,017,000 in 1924, while manufactures were valued a t $1,924,000 as against $1,045,000 in 1924. I n the import trade perfumery, bay rum, and toilet waters amounted to 1,128,000pouhds valued at $2,053,000 as against 1,424,000 pounds valued a t $2,200,000 in 1924. Perfume materials were valued a t $3,388,000 as against 1924 imports of $2,905,000.
Materials Related to Chemical Industries The articles mentioned above comprise the chief items in the trade grouped separately under the heading “Chemicals and Allied Products.” Those following, while not considered as coming under that classification, are more or less closely related to the chemical industries and are of interest to those engaged in these industries. Sulfur
Sulfur exports showed a big gain, amounting to 629,000 tons valued a t $11,000,000 as compared with 482,000 tons valued a t $7,793,000 in 1924. Exports to Germany, 137,000 tons, compared with 80,000 tons in 1924, and were almost double in value. Canada and France were the next best customers. Mineral Oils
The following table shows the exports of mineral oils in the last two years:
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Exports of M i n e r a l Oils -1923 -1924Gallons Value Gallons Value Petroleum, crude 739,405,000 $ 26,495,000 551,246,000 $ 24,274,000 Refined mineral oils: Gasoline. naDhtha.
Explosives, Ammunition, and Fireworks
About three-fifths of our exports of explosives consisted of dynamite, 16,986,000 pounds valued a t $2,444,000, rather more than in 1924. Exports of cartridges were also larger, 5,486,000 pounds as against 5,396,000 pounds in 1924, but lower prices caused a drop of 10 per cent in total values, from $2,916,000to $2,627,000. Imports under this heading are small, consisting mostly of firecrackers. Soaps, Toilet Preparations, Etc.
The United States continued last year to do a very prosperous business in soaps and toilet preparations, the exports of $16,111,000 being 7 per cent higher than in 1924. Of the soaps the chief item was laundry soap, $4,008,000, of which iMexico and Canada were the biggest buyers American toilet or fancy soaps are widely popular and go to all parts of the world, Cuba leading in the trade. Total 1925 exports were 6,750,000 pounds valued a t $2,803,000. Exports of toilet preparations have been grouing steadily in recent years. I n 1925 they totaled $8,078,000 as against $7,252,000 in 1924. Dentifrices were the chief item, amounting to 3,405,000 pounds valued a t $3,211,000, an increase of
TOTAL
4,661,673,000 $418,483,000 4,489,378,000 $445,502,000
The drop in crude petroleum occurred in the trade of all the large buyers except Germany, whose purchases were 60 per cent higher. Canada took two-thirds of the total. Trade in gasoline and other light products was as usual widely scattered. The United Kingdom was much the largest buyer, taking 23 per cent. France was second with 16 per cent, and Europe as a whole took about 60 per cent. Of oil exports for gas manufacture and for fuel, the United Kingdom and Canada each took about one-seventh. Besides the figures given in the table above, oil-burning vessels in the foreign trade loaded as bunker oil 42,827,000 barrels, valued at $68,173,000, as compared with 43,328,000 barrels valued a t $57,973,000 in 1924. I n lubricating oil the United Kingdom led with 22 per cent, followed by France with 17 per cent. Europe took nearly three-fourths. Imports of crude petroleum and refined products fell off in quantity from 3,970,000,000 gallons to 3,287,000,000 gallons in 1928, but rose in value from $100,712,000 to $106,690,000. The decrease in amount was due largely to much smaller shipments from Mexico.
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IXDUSTRIAL A N D ENGINEERING CHEMISTRY
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. I n 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.
T
1
Received October 15, 1925. Awbery, J . Sci. Instruments, 8 , No. 11, 358 (1925).
* Criffiths and
