I,VDrJSTRIAL A Y D ENGINEERIXG CHEMISTRY
July, 1926
703
American Trade in Paints, Varnishes, and R a w Materials’ By Otto Wilson IC
MUNSEYBUILDING,WASHINGTON, D. C.
0 AN unusual degree does the interest of the United States in paints and varnishes lie in the domestic field. We manufacture and use more paint and varnish than any other country in the world. But only a small part of our annual output goes abroad, and our purchases from foreign countries are confined largely to raw materials. Our total foreign sales of paints and varnishes represent less than 4 per cent of our yearly output, and the value of our imports is hardly 1 per cent of that of the products of our own factories. Looking ahead, however, we may expect that the export trade, a t least, will show a continued expansion. It has a promising start in a wide range of markets. Cans of paints and varnishes bearing dmerican labels are known and favorably regarded in every part of the world. Competition from other exporting countries is not so strong as to discourage sales efforts and yet is brisk enough to keep our selling forces “on their toes.” As the interest of American manufacturers in the export field increases we can look forward to a more intensive cultivation of markets which are now little else but geographical names to most of them, with a consequent rise in volume of sales.
T
Domestic Production
The hitherto great preoccupation of American paint and varnish makers with the internal trade is easily enough understood. For the full term of our national life the ,building of houses, factories, bridges, and structures of all kinds has been one of our outstanding activities; and a very large proportion of these structures have been of wood, calling not only for a covering of paint when first erected but for constant renewals. Brick, steel, and concrete construction has been making considerable advance in the larger cities in recent years, but we are still very much a nation living in wooden walls. In country districts few dwellings and fewer outbuildings are of anything else than wood, while in cities and towns of over 2500 population, according to one estimate, 60 to 80 per cent of the dwellings are frame. In this respect we resemble most of the newer countries but contrast with those of Europe, for example, where ancient dwellings of brick and stone, often dating back for .centuries, are the rule. This preference of ours for wooden houses, together with high living standards, has given us our logical place as the greatest consumer of paints and varnishes, and we may look forward to a continuance of the strong demand for many years to come, until the deep inroads in our timber supply are reflected in a much reduced lumber output and a displacement of wood with other materials. The present period marks the highest point to which the production and use of paints and varnishes in the United States have risen. According to an announcement just released by the United States Bureau of the Census, covering the year 1925, there has been little slackening in the activity of our factories since the detailed returns of the biennial census of 1923 were compiled. Those returns showed a total value of manufactured paints, pigments, lacquers, and varnishes in the United States of $440,565,000. Since there has been no general decline in prices it is safe to say that our 1
Received March 30, 1926.
present production is at the rate of about half a billion dollars a year, and it may go well beyond that amount. In only one line of goods has there been a falling off in recent years. That is in paints ground in oil to the form of a paste. Ready-mixed paints, as well as varnishes, japans, and lacquers, have steadily increased in production for many years and now stand at their highest point. Table I shows the volume of output of our factories in the last four years. of Paints and Varnishes in the United States Ready-mixed Varnishes, japans, and semipaste paints and lacquers Gallons Gallons 436,295,000 66,071,000 55,709,000 439,175,000 82,070,000 70,731,000 70,450,000 88,274,000 487,611,000 465,285,000 99,709,000 82,017,000
Table I-Production Year
1922 1923 1924 1925
Paste paints Pounds
The drop in paste paints last year was due to a decline in the output of white lead ground in oil, which made up nearly two-thirds of that item. Our production of white lead prepared in this manner has not shown the steady advance of most other paints and varnishes. Last year’s output, for example, was 10 per cent under that of 1921, and was only about 20 per cent greater in amount than that of twenty years ago, although higher prices made the increase in total value much greater. This doubtless is to be ascribed to the growing popularity of paints put on the market ready mixed for use. These have quadrupled in amount in the last two decades, and the 1925 production of a hundred million gallons was 150 per cent higher than that of the first year of the European War, 1914. Our annual output of varnishes, japans, and lacquers makes up about one-fourth the total value credited to paint and varnish manufactures. No figures of value for 1925 have been announced, but in 1923, out of a total production of paints and varnishes together valued a t $440,000,000, the value of varnishes and similar articles alone represented $113,000,000, and this may be considered a normal proportion. The latter figure, however, did not include a certain amount turned out as by-products of industries not primarily concerned with paints and varnishes, figures for which are not obtainable in detail, but which amounted to about $36,000,000 for paints and varnishes together. The most striking feature of the varnish industry in recent years has been the rapid advance of pyroxylin lacquers. Four years ago, when the 1921 census of manufactures was taken, only seventeen establishments reported the manufacture of varnishes and lacquers made from nitrocellulose. Their total output for that year was 1,409,000 gallons. By 1923 these figures were more than doubled, forty-one plants reporting a production of 3,256,000 gallons. I n the following two years the growth was still more rapid, and in 1925 the number of plants making these varnishes was eighty-five, turning out a total of 11,103,000 gallons. I n four years, therefore, the number of plants interested in this manufacture has been multiplied by five, and the total output has increased eightfold. Last year’s production represented about 14 per cent of the whole production of varnishes in the United States. That the increase still continues is indicated by the government announcement that, while all other varnishes registered a
704
INDUSTRIAL AND ENGINEERING CHEMISTRY
gain of 7 per cent in production in the last half of 1925 as compared with the corresponding period of 1924, pyroxylin varnishes gained lS8per cent’ Because Of a variation, the output of paints and varnishes in the last half of the year is nearly always below that of the first half. In 1925, production in the last six months decreased 7 per cent for paste paints, 10 per cent for ready-mixed and semipaste paints, and 6 per cent for varnishes other than pyroxylin; but the pyroxylin product showed a gain of 27.5 per cent. The chief use of these nitrocellulose lacquers has been as a spray for coating automobile bodies and furniture, and for use to a certain extent on interior woodwork of buildings. For automobiles they have two great advantages. They are very quickly applied, and they are highly durable, giving a finish which resists successfully most of the assaults of mud and weather. At the Baltimore meeting of the Section of Paint and Varnish Chemi s t r y of t h e A M E R I C A N CHEMICAL SOCIETY the head finisher for one of the most popular makes of American automobiles predicted that in two years varnish finishes for a u t o m o b i l e s would disappear entirely. “It used to take ten or fifteen days to finish a car.” he said, “now it takes three. Two years ago we had no r o o m f o r t h e automobile b o d i e s awaiting painting. We had 5000 bodies out in the field that we couldn’t get into our store room. ?sow we have three floors empty Wood Oil Junk i n t h e and are all caught up. We . had 875 painters and now we have 300, and we produce just as many cars as before. The saving amounts to well over a million dollars.’’ So well does the new finish stand up against dust, mud, tar, soap, oil, and ordinary abrasions that complaints of automobile buyers with respect to finish are said to have been greatly reduced or almost eliminated. I n hotels the rapiddrying quality of pyroxylin lacquers has made them valuable for repairing rooms. When a guest moves out any necessary recoating can be done and the room can be occupied again the same evening. Until recently the new lacquer has had to be applied by means of a spray-gun. Many attempts have been made to develop a “brushing” lacquer, and manufacturers are now claiming great success, and are marketing lacquers which they say can be applied with excellent results by brush. European countries are also finding pyroxylin lacquers valuable for finishing and refinishing automobiles. I n England their use is growing rapidly. Last year, according to one estimate, 25,000 to 30,000 gallons were required for the motor-car industry and during the present year it is expected that consumption for all purposes will reach 85,000 gallons. Observers of the trade look forward to an annual consumption in three or four years of some 200,000 gallons for finishing and an equal amount for refinishing. About one-half of this lacquer is the product of one British firm. Prices for the domestic product are said to be lower than for imported lacquer of equal grade. American pyroxylin lacquers are also being marketed in Germany for use on automobile bodies, but high prices are said to hold back sales. A satisfactory domestic product is
Vol. 18, No. 7
being developed which is making headway against the American article. in Value of paint and Varnish product$on in the United Statesa Year Value Year Value 1869 $21,924,000 1909 $124,889,000 1879 29,112,000 1914 145,624,000 1889 54,234,000 1919 340,347,000 1899 69,562,000 1921 274,310,000 1904 90,840,000 1923 404,134,000 a Including only products of plants engaged primarily in the manufacture of paints and varnishes. Paint and varnish as subsldiary products of other industries were valued at $36 430 000 in 1923, $14,387,000 in 1921, $41,569,000 In 1919, and $3,550,000 id 19i4. Table II-Growth
The extent to which these Smerican lacquers have found a market in Europe is a matter of estimate only, as government trade statistics do not list them separately. Our foreign sales, however, have naturally been and will continue to be merely incidental to the rapidly expanding trade in our domestic market. L o o k i n g back over the past fifty years, it will be s e e n t h a t the paint and varnish industry generally has kept fully abreast in itls development with the marvelous advance in national w e a l t h and industry in that t i m e . C o m p a r i n g present p r o d u c t i o n w i t h that shown by the official returns for 1569, we find our output today t o be twentyfive times as great in value as it was then. Since the b e g i n n i n g of the present century the value of the The Werner G. Smith Co. products of the paint and Upper Yangtze River varnish industry has increased seven times over. Government figures covering the output of the industry over half a century of growth will be interesting (Table 11). In the years since the late war the industry has experienced a remarkable growth. Manufacturers of paints and varnishes are now receiving three times as much money for their wares as they did before the war, due partly, it is true, to prices 70 or 50 per cent higher, but also to greatly increased volume. A‘ote-In 1923 the average value of paints ground in oil, manufactured in the United States, was 7 cents, in 1914, 4 cents; of ready-mixed oil paints, 51.78 per gallon in 1923, and $1 02 in 1914; of water paints and kalsomine, dry or in paste form, 5 cents per pound in 1923 and 3 cents in 1914, of varnishes, japans, and lacquers, $1 45 per gallon in 1923 and 88 cents in 1914.
Production of paints and varnishes, dependent as they are on other industries for their field of usefulness, follows closely the ups and downs of general business. Immediately following the war, it will be remembered, came a period of intense and almost feverish business activity, characterized by an inflation which was anything but economically healthy. This was followed by the severe depression of 1920 and 1921, and then by a gradual recovery to our present high level of prosperity. Paint and varnish manufacture has run along with these waves of business activity. It has been particularly affected by the large amount of construction in evidence in the last few years which has been gradually filling in the hole left by the suspension of building during the war period. As the country catches up with its building program it is reasonable to expect that there will be a tapering off in the demand for paints and varnishes which may hold back for a while the rate of growth evident in the last few years.
J u l y , 1926
I X D CSTRIAL A X D EXGINEERING CHEMISTRY
Both the manufacture and the consumption of paints and varnish in this country center in a group of states which includes New York, Pennsylvania, New Jersey, southern Xew England, Maryland, and Delaware in the east, and Ohio, Indiana, Illinois, and Michigan in the midwtlst. These states furnish the market for about one-half the American output, and most of the larger factories are found within their borders. Considering all the branches of the industry, S e w York may be assigned the place of leading state in paint and varnish production. Illinois, Pennsylvania. New Jersey, and California are among the leading producers.* Export Trade
As noted above, the export trade occupies a place of but minor importance in the American paint and varnish industry. I t is much greater now than before the war, the total value being twice or three times the pre-war average; but it is a fluctuating trade and is still to be regarded in part as an overflow from the domestic markets. The fact that it is so widely scattered is a promising feature, as the seed thus broadcast over the earth may be expected to grow a goodly crop as the newer and less advanced regions develop. The chief obstacle to American trade expansion abroad is the domestic industry of the various countries, which often supplies most or all of their needs. Among exporting nations Great Britain is our chief competitor. Germany has a place of some prominence in many markets. In the aggregate value of annual exports of manufactured paints and varnishes Great Britain is considerably ahead of the United States. I n the paint trade, however. the larger part of her exports go to the various parts of her own empire, Ireland, India, iiustralia, New Zealand, and South Africa. Out of a total value of paint and pigment exports in 1924 of f1,176,000 more than half, or &655,000, went to countries within the empire arid f521.000 to foreign countries. Of the varnish exports, however, foreign countries took $436,000 out of a total of &763,000. Because of imperial preference American exporters cannot meet the British on even terms in these markets. But in neutral markets American wares for the most part hold their own. I n near-by places like the West Indies the American product dominates except in the islands owned by the British, French, and Dutch, where the larger part of the requirements are supplied by the mother countries. Even in these dependencies, hoh-ever, ilmerican goods are making their way. In Trinidad, for example, American varnish outsells both the British and the Canadian products.3 In the South American countries British and American paints and varnishes are brisk competitors. Our natural advantages in some of these markets are offset, in part a t least, by a factor whirh has appeared in many other lines of export trade-our lack of a keen interest in exports because of the engrossing character of our domestic trade. This, say the trade commentators, has led to such inattention to details as the packing of paints in heavy containers when shipping to countries where the rate of duty on the contents applies also to the container and to a careless change in labels on goods sent to markets where the buying is by trademarks and brands. European shippers give more attention to these details because of long acquaintance with market requirements. However, these are minor objections and they have not prevented the growth of American business to a comparatively good volume. 4 Those who wish t o make a study of the distribiition of our paint trade will find a n interesting analysis of t h e domestic market in a pamphlet issued b y t h e Chemical Division of t h e Department of Commerci as Domeslzc Commerce Serres hTo 2, b y Priest. These markets have been made t h e subiect of a special study by the Department of Commerce in Trade Informalson Rullrlsn 341.
705
Outside of our next-door neighbors Argentina offers the field of most present interest to exporters. Our wares meet strong competition there from the British, and the Germans make a good third. Future building prospects in Argentina are good, and the outlook is promising for an expansion of the present trade. In the Far East our best customer is Japan, with China and the Philippines following. Japan supplies herself with most of her own requirements in paints and varnishes, but buys heavily from us in pigments, particularly carbon blacks. Japanese manufacturers, it is said, have not yet learned how to make good noncorrosive paints and most of her requirements in that line are imported. China and the Philippines, on the other hand, are most interested in our prepared paints and varnishes. Exports of paints, pigments, and varnishes from the United States are about equally divided between pigments, mineral and chemical, and prepared paints and varnishes. Table 111 shows the trade of the last two years. Table 111-Exports
of Paints Pigments and Varnishes from the United States' -1924Quantity Pounds
Value
Mineral earth pigments-ocher, umber, sienna, metallic whiting, etc. 28,207,000 S 824,000 Chemical Diements: Zinc oxi'de 7,864,000 606,000 Lithopone 1,846,000 106,000 Bone black 1,972,000 123,000 Bone black a n d lampblack .. . . Carbon a n d lampblack 34,429,000 3,386,000 Carbon black Red lead 1,880,'OOO 21'1',000 White lead 10,109,000 853,000 Other chemical pigments 5,156,000 614,000 Paints, stains, and enamels: Enamel paints 1,875,000 483,000 Other ready-mixed Gallons 2,016,000 4,030,000 paints Pounds 8,383,000 1,485,000 Other paints Varnishes: Gallons Oil varnishes 652,000 1,123,000 Other varnishes 284,000 483,000 TOTAL . 14,326,000
....
.. .
-192Quantity Pounds
31,267,000
Value
5
904,000
21,710,000 2,573,000
1,504,000 133,000
3,804,000
250,000
43, iii,'ooo 1,604,000 13,663,000
3, ,iis;ooo 184,000 1,293,000
.. . .
....
6,526,000
760,000
2,663,000 Gallons 2,237,000 Pounds 11,438,000 Gallons 712,000 395,000
882,000
.. ..
4,658,000 2,363,000
.
1,279,000 745,000 18,511,000
As these figures show, our most popular products are enamels and ready-mixed paints, which comprise more than a fourth of the total sales. Cuba, Mexico, and Canada are perhaps the leading buyers, year in and year out, but the trade also reaches out to the far ends of the earth. Last year Argentina led the list of customers in the trade in enamel paints, taking 437,000 pounds, with Australia second, with 322,000 pounds. Cuba purchased from us 630,000 gallons of other ready-mixed paints, more than one-fourth of the total exports. Argentina, with 189,000 gallons, was second, her purchases being valued a t 5509,000. Other paints went to a long list of buyers with Canada and Cuba a t their head. The trade in varnishes is rather fluctuating. European countries are prominent buyers, especially the United Kingdom, which in 1925 imported from the United States 129,000 gallons of oil varnishes out of our total exports of 712,000 ga!lons, and 30,000 gallons of other varnishes out of a total of 395,000 gallons. France, Italy, and Belgium are well up in this trade, as are also Argentina and Brazil in South Bmerica and Japan in the East. The chief export trade in pigments is in carbon blacks, a large part of which, however, go into other industries than paint manufacture. Last year one-third of our exports of this article went to the United Kingdom, which country also took a fourth of the exports of bone black and lampblack. Following the United Kingdom as buyers of carbon black were
INDUSTRIAL A N D ENGINEERING CUEiMISTE Y
706
Gerinaiiy, with 17 per cent of the total, and France, with 16 per cent. Canada and Australia were also prominent in this trade. In the trade in ocher, sienna, umber, and other mineral eartli pigments, Canada was niuch the heaviest pur-
9,743,000 pounds and Canada S,640,000 pounds. I n spite of a strong prejudice against lead paints in Europe, because of a belief that they arc poisonous to laborers, the greatcr part of United St.ates exports of white load go t,o European countries. Shipments in 1925 to the United King. dom amounted to S,349,000 pounds, or 60 per cent of the total exports, having a value of $734,000. Tlie Net,herlands figured in the trade to the extent of 967,000 pounds and more distant markets were represented by Argentina 1,838,000 pounds and the Philippines with 450,000 poun In addition to manufactured products, our foreign sa ilaval stores bring in a return twice as large as that of all paints and varnishes put together. A notable feature of the 1925 export trade in rosin was the big increase of nearly 40 per cent in total value BS compared with 1924, while the act u d ainount shipped decreased 20 per were 1,172,000 barrels valued a t $18,889,000 1,452,000 barrels valued a t $13,755,000 for much higher prices had the double effect of curtai consumption and causing foreign buyers to t u sources. French producers particularly the new demand, and rosin exports from 42,000 tons in 1924 to 63,000 tons in 192 to more than 100,000 American barrels. half our exports of rosin went to Europe, the United Kingdom alone t a k i n g 263,000 barrels, or 22 per cent. A l t h o u g h e x p o r t s of s p i r i t s of t u r p e n t i n e s e mained ahout the same last year as in the year before, 11,557,000gaUonsasagainst 11,510,000gallons, thevalue was about one-eighthhigher, the average price being 98 cents as against S8 cents. This rise was also reflected in much larger sales by the F r e n c h , \+ho exported to f o r e i g n c o u n t r i e s 13,000 tons in 1925 as against 8600 tons in the year before. The higher prices, however, did
turprntine. larger than
Exports to
111 1924.
Import Trade
In the import trade the purchases o aud varnishes by the United States
Vol. 18, No. 7
product, wood or nut oil. India contributes the all-important shellac, sending to American ports half her annual supply. From the Antipodes comes the valuable kauri gum, and from the Dutch islands of the Pacific its near relative, damar. These are all of basic importance to manufacturers, and the size and value of the annual importations are a measure of the extent to which the United States still falls short of selfsufficicncy in the paint and varnish industry. If neoessaly, tho biggest import of all could be supplied out of our own soil. This is flaxseed, which Argentina and Canada send in varyiiig quantities to supplement the domestic output. Tlie relative proportions of imports and domestic produetioii of flaxseed fluctuate widely from year t,oyear. At times the United States imports more than it raises, and at other times the reverse is true. Until about the beginning of the present cent.ury this country not only supplied its own needs ed but exported considerable quantities. ion then declined steadily and that of C
crop, and in 1924 and 1925 imports were wcll below domestic ative figures for the last six years are tic Production of Flaxseed in
n fed States
cent of the seed tine are heavier t
INDUSTRIAL A N D ENGINEERING CHEMISTRY
July, 1926
improve quality and output. They remember how synthetic indigo brought disaster to a former prosperous and flourishing industry of India, and they are taking steps to try to avert a similar fate for natural lac. Imports into this country, which for the most part come direct from India, have remained fairly steady in amount, but the value has fluctuated very widely. Before the war the average import valuation was 14 cents per pound; since the war it has gone as high as 80 cents, and it is now about 50 cents. Table V-Imports Average 1910-14’ 1919 1920 1921 1922 1923 1924 1925 a
of Shellac into the U n i t e d States Pounds 20,455.000 24,426,000 28,587,000 27,841,000 25,163,000 38,447,000 24,553,000 19,913,000
Value f 2,843,000 11,869,000 23,089,000 13,618,000 14,916,000 22,955,000 13,139,000 10,164,000
Fiscal years.
More than the shellac industry has the industry handling another prized varnish gum, kauri, felt the competition of the rising synthetic lacquer. Kauri is found in only one small region of the world, northern New Zealand. It, is a fossil resin from forests buried ages ago by volcanic action. In the past it has been in much demand as a base for the finer grades of varnish, and one of its important uses has been in finishing automobile bodies. Much the larger part of the exports from K\‘ew Zealand have come to the United States, the other important buyer being the United Kingdom. Not only has the quantity of our purchases been decreasing but the price has also fallen. In 1923 this country imported 8,917,000 pounds of kauri, valued a t $2,018,000, the average value per pound being about 23 cents. I n 1924 importations dropped to 5,869,000 pounds valued a t $1,102,000, an average valuation of less than 19 cents. Last year they amounted to only 4,634,000 pounds valued a t $813,000, or slightly more than 17 cents per pound.
70 7
This decline, together with an increasing production cost as the more accessible gum is dug out, have caused the New Zealand Government to put the whole industry under the control of a special government board. It was expected that this control would date from about April 1, 1926. The board has wide powers, and will endeavor to reduce production costs, push the use of kauri, and keep prices from going to unprofitable levels. Imports of damar, also a valuable varnish base, do not seem to have been affected by pyroxylin lacquer production. They were 12,697,000 pounds valued a t $1,569,000 in 1925, as against 9,626,000 pounds valued a t $1,088,000 in 1924 and 11,484,000 pounds valued a t $1,482,000 in 1923. The chief sources are the Straits Settlements and Java and other islands of the Dutch East Indies. China’s greatly esteemed contribution to our varnish industry, variously known as wood oil, nut oil, and tung oil, continues to find a ready welcome on the American market. The 1925 imports of 101,000,000 pounds valued a t $11,386,000 were greater by 25 per cent in quantity than those of 1924, although the total value showed a much smaller rise. In the last twenty years this oil has come into widespread use, especially in varnishes intended to be particularly waterresisting and durable. China has a complete monopoly of its production. It is the product of a widespread native industry in that country, the export trade centering in Hankow. From 50 to 80 per cent of the annual production comes to the United States. Experiments in raising tung oil trees in the United States have been carried forward for many years, with varying degrees of success. The most promising venture is a t Gainesville, Florida, where 2000 acres have been planted with 200,000 trees. The experiment has not yet gone far enough for the ultimate economic status of the industry in this country to be definitely forecasted, but it gives good promise of success.
~~
Mercuric Bromide Paper for the Gutzeit Method for Arsenic‘ By Geo. Kemmerer and Helmuth H. Schrenk UNIVERSITY
OF
WISCONSIN^ MADISON,WIS.
HE Gutzeit2 method for t h e determination of small amounts of arsenic has been carefully studied and widely used, b u t with constant use for routine work in this laboratory the results were not so reliable a s is desired. In the first place the length of t h e color bands produced by equal quantities of arsenic varied greatly, although all of the known precautions were taken. In addition the color bands were often uneven or spotted. These difficulties occurred using the regular procedure3 and a 1.5 per cent solution of mercuric bromide4 dissolved in 95 per cent alcohol as a sensitizing solution. The work was started b y trying various sensitizing agents in water and alcoholic solutions. After numerous trials i t was decided t h a t the alcoholic solution of mercuric bromide gave the best colors, especially with small amounts of arsenic. Several grades of filter and drawing paper were used to absorb the sensitiaing solution. Whitman No. 40 and other soft, wellwashed quantitative filter paper gave good results, b u t the colored bands still varied in length and were often spotted. Some of the paper strips t h a t had been treated with the mercuric bromide solution were then dried in a n electric oven at from 50” t o 105’ C. Others were dried in desiccators over calcium chloride, sulfuric acid, and barium bromide. The time of drying over each was varied from a few hours t o several days. Most of these tests gave poorer results than the simple drying Received April 19, 1926. Pharm. Zlg., 1879. 8 Scott, “Standard Methods of Chemical Analysis,” 4th ed., 1925, Vol. I, p. 52. 4 Sanger and Black, J . SOL.Chcm. I n d . , 26, 1115 (1907). 1
2
of the strips in the air, b u t t h e tests proved definitely t h a t the presence of more than traces of moisture and the uneven distribution of the moisture tended to produce uneven colors and t h a t long drying or storing of the treated strips or drying a t high temperatures produced dim poor colors. With this in mind i t seemed necessary t o control the moisture content of t h e strips more definitely. A t this point i t was noticed that, using the regular method, the results were better during the dry, cold winter weather and became more uneven as spring advanced. This again suggested t h e importance of moisture in the sensitized strips of paper. Since the moisture in the sensitizing solution used here is limited t o the 5 per cent present in the alcohol (most of which would evaporate with the alcohol) any variable moisture must be present in the paper before i t is treated. The Forest Products Laboratory6 has shown t h a t the water contained in paper which appears dry varies greatly. To remove this water the untreated filter paper was dried a t 105’ for one hour and stored over calcium chloride until needed. PROCEDURE-The regular Gutzeit apparatus and procedure are used except t h a t the paper which is to be sensitized is dried a t 105’ C. for 1 hour and stored in a desiccator over calcium chloride. This paper is then cut into 4-mm. strips and saturated with a 1.5 per cent solution of mercuric bromide in 95 per cent ethyl alcohol. These are allowed t o drain and are then dried in a large desiccator for 10 minutes and used. No treated strips should be stored longer than 2 hours before use. The method has been used for routine work in two laboratories for one year with a marked improvement in results. 8
“How Paper Is Affected by Humidity.”
