October, 1927
I S D U S T R I A L .4SD ELVGI.VEERISG CHEMISTRY
I-Unsaturated hydrocarbons play a n important role in the oxidation of transformer oils. 2-There is a definite relationship between the quantity of sludge formed and the unsaturated hydrocarbons as measured by 95 per cent sulfuric acid absorption. 3-The oxidation of saturated hydrocarbons is retarded by the presence of unsaturated compounds. 4-Small amounts of unsaturated hydrocarbons retard oxidation only temporarily and finally large quantities of sludge are precipitated. 5-With oils containing over 5 per cent unsaturated hydrocarbons the quantity of sludge formed appears t o be independent of the base of the oil. 6--illthough the method for the determination of naphthenes is not entire6 free from error, it is of value for determining the approximate source of an oil and for showing how it will act under certain conditions.
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7-High molecular weight naphthene hydrocarbons do not appear to be so sensitive t o oxidation as those of low molecular weight. &Mixtures of high molecular weight naphthene with paraffin hydrocarbons give an oil with high resistance to oxidation. 9-No general rule can be given concerning the effect of different temperatures on the rate of oxidation of different oils. 10-Temperatures other than operating temperatures will give false results with certain oils. 11-From the analysis and oxidation tests herein described, one may predict the approximate behavior of a n oil at a definite temperature.
Acknowledgment The author is indebted to D. R. Kellogg and his associates who were of assistance in facilitating this work.
Stainless Iron and Its Application to Chemical Plant Construction’ By Walter M. Mitchell CENTRAL ALLOYSTEEL CORPORATION, MASSILLON.OHIO
N
OT many years ago the metallurgist had recourse to the
chemist for solution of the problems encountered in the development of metallurgical processes; and now, in turn, the chemist finds it necessary to consult the metallurgist when problems concerning the selection of materials for specific purposes are to be solved. The selection of materials suitable for the construction of apparatus for the manufacture of corrosive products is one of the major difficulties experienced in many of the developments in chemical industries, and no process of chemical manufacture can be considered as satisfactorily established until a suitable material has been found in which the reactions involved can be carried out on a large scale. I n the past this subject has perhaps been overlooked, but with the newer synthetic processes involring very high temperatures or pressures, frequently both, the materials of construction become vitally important. The advent, therefore, of a class of alloys with high strength, obtainable in virtually all necessary shapes, possessing good general corrosion resistance, and high specific resistance to a definite class of compounds, has naturally been heralded with considerable enthusiasm. This class of alloys comprises the so-called “stainless” irons and steels, the characteristic properties of which are due to the presence of a considerable proportion of chromium-a white, hard, somewhat brittle metal, noted for its high melting point and its resistance to oxidation and oxidizing agents. Commercial Development
It would be interesting to trace the development of these alloys from the time of Faraday and Stodart, who in 1820 were the first to experiment with the addition of chromium to iron, to the products of the present time, but we are not so much concerned with the historical development as with the practical application of the alloys at present produced. It is sufficient to note that the earliest experiments with the addition of chromium to steel were with the idea of its substitution as a hardening element in place of the more customary carbon. We know today that chromium confers no hardening properties in itself, but merely forms a solid solution with the iron. The earlier experimenters noted that the alloys of iron rich in chromium were hard, fused with difficulty, 1 Presented before the meeting of the Indiana Section of t h e American Chemical Society, South Bend, I n d , April 20, 1927.
resisted oxidation and atmospheric attack, and in addition were not attacked by a number of chemical reagents, the most prominent of which was nitric acid. The first commercial development of these alloys, making use of their corrosion-resisting qualities, appears to have been due to Harry Brearley, of the laboratory of Thomas Firth and Sons in Sheffield, England. Brearley conducted an extensive research to determine resistance to erosion of various types of steels with reference to their use for rifles and naval guns. Certain of these steels carrying high chromium were not attacked a t all, or only very slowly, by the usual metallographic etching reagents, nor were the specimens rusted after months’ exposure to the atmosphere of the physical laboratory. The ultimate outcome of this was the marketing of the now familiar “stainless steel” containing 11to 13 per cent chromium with 0.30 to 0.35 per cent carbon, as a t present used for cutlery, surgical instruments, etc. Patents were eventually applied for, and later granted in Canada in 1915 and the following year in the United States, Specific claims covered the composition of the alloy, also the necessity for heat treatment and the preparation of a polished surface to produce full stainless qualities. At about the same time Elwood Haynes, of the United States, was granted a patent for a ferrous alloy containing high chromium, disclosing the “noble” character of the polished surfaces of wrought-metal articles of the composition specified. This is a broader and more generic patent covering stainless materials in general, while the Brearley patent may be considered as covering a specific product included in the broader classification allowed to Haynes. Probably the most interesting of the patents granted, and it may eventually develop, because the date of application precedes the above patents, that they are also the most important, are the Strauss patents, granted in 1919 and 1920 in the United States covering alloys containing nickel (0.5 to 20 per cent) in addition to chromium (6.0 to 40.0 per cent). Both these patents and the British Pasel patents emanate from the same inventor, who a t the time was a member of the staff of the Krupp gun works a t Essen. Practically all the straight iron-chromium alloys which had been produced in a commercial way up to this time contained sufficient carbon to confer hardening properties and the “stainlessness” was only developed after proper heat
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treatment. This was more or less unintentional and merely a consequence of the inability a t that time to produce a very low carbon, or carbon-free, ferrochromium alloy, used as a means of introducing chromium into this steel. This, of course, is a result of the tremendous affinity of carbon for chromium. These alloys (with the exception of the nickelchromium alloys) were true steels in that they were capable of hardening by heat treatment. The necessity of heat treatment arises through the formation of iron-chromium carbides if any considerable proportion of carbon is present in the alloy. These carbides have a solution potential different from that of the matrix of ironchromium solid solution and hence electrolytic action will take place between the carbides and the solid solution. When the alloy is heated above the critical range the carbides dissolve in the solid solution and if cooling is sufficiently rapid will remain in solution, the alloy being virtually homogeneous. Annealing with very slow cooling allows the carbides to precipitate out of solution as “free” constituents, and the alloy is subject to corrosive attack as before. The natural limitations of the stainless steels-that is, the necessity for heat treatment to produce corrosion resistance, and their hard, uncompromising character, obviously useful in cutlery but practically useless as a material of general utility-led to the development about 1919 of the “stainless irons” containing a very low percentage of carbon. The stainless irons possess a decided advantage because, with low carbon, they are virtually free from the presence of carbides, and hence are practically equally corrosion-resistant in any condition. I n addition they are tough and strong and may be produced in many shapes for which the harder steels are totally unsuited. I n 1919 Armstrong was granted patents in the United States covering an alloy containing chromium, carbon, and silicon, claiming an alloy of “high surface stability.” The range of composition, however, was afterward restricted by court decision to carbon less than that of Haynes, with chromium greater than that of Brearley, the addition of silicon remaining. Thus, there was developed an alloy containing relatively high chromium, very low carbon, and a moderate percentage of silicon. This closely approximates a true stainless iron and possesses many valuable properties, which will be discussed later. Naturally, other alloys of somewhat similar composition have appeared, following as closely as patent specifications will permit the modified alloy of Armstrong. Types of Stainless Alloys
As a result of the variations in physical properties imparted by additional elements in the composition, and the division of the composition ranges by patent specifications, a series of different types of stainless alloys has logically developed. The most important of these are as follows: 1-The original “stainless steel” of Brearley and Haynes, with a practical composition range of 11 t o 13 per cent chromium and with sufficient carbon t o confer hardening properties, usually 0.30 to 0.40 per cent. 2-The “stainless irons,” a modification of the above with similar chromium, but less carbon, usually under 0.12 per cent. These are virtually mild stainless steels, and when first brought out were heralded as non-hardening. They do, however, possess distinct hardening properties, although not t o the extent of Type 1. 3-The alloys with over 16 per cent chromium and low carbon (usually under 0.10 per cent) with or without small additions of other elements. These are more nearly true stainless irons a s they have very little hardening capacity. 4-The nickel-iron-chromium alloys, the composition ranges of which may vary considerably. 5-High-chromium alloys containing upward of 20 per cent chromium and with medium or high carbon, and without the addition of appreciable percentages of other elements.
Vol. 19, No. 10
TYPE 1-The true stainless steels are rather limited in application in chemical plant construction. Their great hardness, and the fact that they harden rapidly on cooling in air, even while still at a high temperature, limits theii workability, so that the production of intricate shapes and sections together with sheets is practically impossible. Alloys of this class are hard and strong, but have no great toughness or ductility. The physical properties of a typical material are shown in Table I. These properties make this type of alloy useful when hardness and resistance to wear are desirable qualities, such as for valve seats and disks, wearing parts of grinding and crushing machinery, agitators, etc. As has been noted, full corrosion resistance is not obtained until properly heat-treated. Owing to the precipitation of the carbides, corrosion resistance begins to diminish if tempering of the quenched or hardened material is carried above about 500’ C. TYPE2-The general composition of the mild stainless steels is chromium 11 to 14.5 per cent with carbon under 0.12 per cent (sometimes 0.18 per cent is the limit). This is a much more tractable material and may be produced commercially in practically all forms. Seamless tubing has been produced from this analysis, but the production is not so successful as with Type 3. However, sheets, plates, bars, flats, strip, etc., are available in commercial sizes; also rivets, screws, bolts and nuts, wire, etc. Consequently, the construction of tanks, autoclaves, retorts, and similarly fabricated apparatus is readily accomplished. But, owing to the air-hardening properties of the material, due care must be exercised in hot-working operations, such as forging, riveting, etc., if brittleness is to be avoided. This material has excellent physical properties (Table I), its strength several times exceeding that of ordinary structural steel, and it is softer and more ductile than the previous type. As the carbon content of these alloys is relatively low, the variation in corrosion resistance between heat-treated and annealed material is distinctly less than with the regular stainless steel. This material is tough and strong, and in the heat-treated condition is suited for valve fittings, stems, pump rods and plungers, shafting, etc. It will resist oxidation up to about 8OCk825” C. indefinitely. Strength is also well retained a t high temperatures. TYPE3-The true stainless irons, with upward of 16 per cent chromium and carbon under 0.10 per cent, are probably best suited for general purposes of fabrication. Since the corrosion resistance of any of the whole group of alloys depends upon the ratio of chromium to carbon content, the greater the chromium (or its equivalent) the greater the resistance. However, there is a limit beyond which the advantage gained does not compensate for the somen-hat undesirable qualities of materials with very high chromium from the manufacturing and mechanical standpoint. With very high chromium the material becomes increasingly difficult to work, laminated structure in plates and sheets is likely to occur, and beyond increased resistance to oxidation at high temperatures no great advantage is gained. Alloys of Type 3 appear to possess maximum general corrosion resistance consistent with high physical strength, low cost, and ease of workability. While strength is not so great as the Type 2 alloys, it is sufficient for all construction purposes and corrosion resistance is distinctly higher. The addition of a small percentage of silicon with chromium 16 to 18 per cent is undoubtedly beneficial as regards working properties, and corrosion and oxidation resistance a t high temperatures are increased. Silicon will usually run from 0.80 to 1.10 per cent and alloys of this particular analysis have so far had the greatest application in chemical plant construction, es-
Table I-Physical
TYPE
-
COMPOSITION
C
SI
Cr
%
%
%
%
t
0.37
0 20
12.0
0.41
2
0.10
0 19
11.5
0 35
Ni
0.60t00.90 16.5t018.5 0.21
Under0.10
3
Properties of Typical S t a i n l e s s Iron Alloys TENSILE YIELD ELONGATION REDUCTIONBRINELL TREATMENT STRENGTH POINT -(2 INCHES) O F AREA HARDNESS Lbs./sq. in. Lbs./sq. in. % 70 Ouenched a t 900' C. and tem200.000 200.000 9 25 480 pered a t 500' C. ( a ) Oil-quenched a t 950' C. and 180,000 160,000 18 50 35C tempered a t 450' C. I:b) Annealed a t 800" C. 73,000 40,000 37 75 150 ( a ) Hot-rolled bars annealed 75,000 t o 55,000 to 30 to 35 65 to 75 150 to 170 80,000 60,000 I(5) Cold-drawn bars 90,000 to 85,000 to 1 2 t o 15 55 t o 60 200 to 228 95,000 90,000
-
( c ) Annealed sheets and plates
4(a) (b) (6)
5
0 . 5 0 to 1.50
20 to 25
(Krupp type)
10 to 11 S to 9
20 per cent chromium or over
(English type) (a) United States and England, hot-rolled ( b ) Annealed Rolled
Tank plated Castings
(a) Type 5, annealed
0.30 to 0 . 4 0
0.10 0 . 2 0 to 0 . 3 0
1.25 0 . 3 0 t o 0.50
7 to 15 15 t o 16 18 to 20
(5) Type 3, annealed a
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October, 1927
75.000 t o 85.000 100,000 t o 125,000 120,000 120,000 90,000
80,000 to
90,000 60,000 40,000 t o 50,000 95,000 t o 100,000
50,000 to 16 to 22 60.000
75,000to 2 0 t o 3 0 90,000 40,000 70,000
57 35
43,000 60 60,000 to 10 to 25 65,000 40,000 25 30,000to 1 40,000 65,000 to 19 to 22 75,000
40 to 55
200 to 250
50 50
150 to 170 250
75 15 to 30
50 2 30 t o 35
170 170 t o 6OOD
200 170 to 180
Depends on carbon content and heat treatment
b Minimum requirements.
pecially for resistance to nitric acid. Silicon also acts in opposition to carbon and reduces the air-hardening tendency; too high silicon, however, tends rapidly to increase grain growth a t high temperatures, which results in loss of strength and resistance to shock. One great advantage of this type of alloy is the almost complete lack of hardening tendency. Cold-working, however, increases hardness and tensile strength, and when greater hardness is necessary this may be resorted to. These alloys are quite ductile, may be formed, stamped, and deep-drawn cold, and they were the first of the stainless alloys to be produced commercially in the form of seamless drawn tubing. Physical properties, while not so high as the preceding type, are ample for all purposes (Table I). Because of the high chromium content, alloys of this type retain their strength satisfactorily at high temperatures and we find the following stresses withstood without deformation under continuous loads a t the temperatures given: c. 480 540 590 650 705
L b s . p e r sa. in. 32,000 16,000 8,000 6,000 3,000
Alloys of the composition of Type 3 will resist oxidation up to 870-950" C., depending upon the chromium content, indefinitely under continuous service, while under intermittent service they will give long life at considerably higher temperatures. TYPE4-There are a number of what might be called "quasistandard" compositions of the nickel-iron-chromium combination. Metallurgically considered, the useful alloys are all austenitic, and in consequence non-magnetic, and cannot be hardened except by cold-working. These alloys have a number of advantages and are rapidly becoming more popular, and it is not improbable that the ultimate stainless alloy for general use will be of this type. The chief drawback is the increased cost due to the high nickel content; and, being harder and tougher a t high temperature^, they offer more difficulty to production in mill operations, and this also tends t o increase cost. Physical properties will vary somewhat depending upon analyses (Table I), The signal advantage of the nickel-iron-chromium alloys is the ease with which they may be welded, and on account of the absence of any tendency to harden the weld remains
ductile; furthermore, it does not become coarsely crystalline as with straight iron-chromium alloys. The nickel-iron-chromium alloys are generally available in sheets, plates, bars, etc. Some seamless tubing has been produced, but the metal has a tendency to harden in coldworking so that drawing is difficult. TYPE5-The alloys of the fifth type-those with 20 per cent chromium or over-are rather a special type and particularly useful when resistance to oxidation at very high temperatures is demanded. The usual commercial alloys contain 25 to 30 per cent chromium, and may be expected to withstand temperatures as high as 1180" C. under long service. Alloys with low carbon have no particular tendency toward hardening, but those with high carbon become exceedingly hard and tough and may be classified among the hardest materials known. Naturally, they possess great resistance to wear and abrasion. Low-carbon alloys are available in sheets, plates, bars, etc., but are liable to show undesirable laminated structure. Production of the high-carbon sblloys is limited to castings only. Physical properties of rolled material (low carbon) are shown in Table I. Requirements of an Alloy for Chemical Plant Construction I n considering any of the above alloys from the standpoint of utility in the construction of chemical plant equipment, there are three important requirements that must be carefully considered. (1) The corrosion resistance of the material-i. e., what substances do not attack it, and hence for what processes it may be used. (2) The strength of the material; to be considered in order that the apparatus will not fail under actual plant operating conditions. (3) Availability in the required shapes and forms, whether plates, sheets, rivets, tubing, etc.
CORROSION RESISTANCE-Obviously, the first point to be determined is the suitability of the alloy for the purposedoes it have proper corrosion resistance? Laboratory corrosion tests give valuable information, but owing to the difficulty of reproducing actual plant conditions in such tests they should be considered as a first approximation only. I n every case actual plant tests should follow, and whenever possible a small-scale installation should be made in order that the question of chemical suitability may be definitely settled.
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I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
The chief characteristic of the chromium alloys is resistance to nitric acid and oxidizing agents in general, sulfides and similar sulfur compounds, and the milder organic acids. Caustic alkali solutions and solutions of alkali carbonates do not attack. Halogen compounds-chlorides, iodides, bromides, etc.-generally attack the low-chromium alloys, but with high chromium, 16 per cent or over, the attack will be considerably reduced, or there may be no appreciable attack. Ordinary stainless steel of Type 1 analysis is slowly attacked by dilute nitric acid. With stainless iron-low carbon and chromium over 14 per cent-there appears to be no attack by nitric acid in any concentration up to about 80-85' C. The stainless alloys are unquestionably the best metals for equipment for the manufacture and handling of pure acid-that is, acid produced by the oxidation of ammonia process. Acid produced from Chile saltpeter usually contains a small proportion of hydrochloric acid and the amount of this which may be present without producing any effect upon the metal is somewhat uncertain. Apparently, about 0.2 per cent based on nitric acid content is the limit for alloys with 16 per cent chromium. Alloys of Type 4, notwithstanding the nickel content, are not attacked by nitric acid,.provided chromium is maintained over 14 per cent, and when in contact with straight chromium alloys are generally cathodic, the chromium alloys being attacked. Sulfuric acid attacks stainless alloys in all concentrations up to about 95 per cent, but the action may be inhibited when sufficient ferric and cupric sulfates are present in the solution. On this account the stainless chromium alloys have been used with success in handling acid mine waters. The so-called "mixed acid," a combination of sulfuric and nitric acids, in general does not attack the high-chromium alloys. STRENGTH-The second requirement can be dismissed without hesitation. All these alloys have high strength, greater than the steels ordinarily used, and unless defective material is unintentionally supplied, designs for equipment to be made of steel will be entirely suitable for the stainless irons, I n fact, owing to their greater strength it may be possible in many cases to use lighter weight materials. Naturally, materials ordered for plant construction should be subjected to careful inspection and testing to give assurance that material of good quality is supplied. AVAILABILITY IN NECESSARY SHAPEB AXD FORMS-This requirement may offer some difficulty in certain particulars. It is important, in order to avoid electrolytic action, that all parts of a given piece of equipment be constructed as much as possible of the same material. I n the presence of even nitric acid alloys of Type 2 are anodic as compared with Type 3, and with more energetic attacking agents the difference in solution potential may be sufficient to render the equipment unsafe. The procurement of large-size plates, etc., of stainless alloys of various types other than Type 1 has presented no serious difficulty, once the peculiar characteristics of the alloy have become known to the practical mill man. Single-piece flanged and dished heads up to 10 feet in diameter have been made, and the sizes possible appear to be limited only by the equipment available for their production. Sheets are also available in the usual commercial sizes and gages; very light gages, however, we not yet a commercial product in larger sizes. Considerably lighter material is available in strip form, down to 0.003-inch thickness but in narrow widths only. Materials for tank plates should show the minimum physical properties, as given in Table I. To avoid brittle mate-
Vol. 19, No. 10
rial a bend test should also be made. A standard plate specimen should withstand bending 120 degrees without fracture. Actually, any of the alloys described above, with the exception of Type 1, or possibly Type 5, should be capable of being bent flat on itself cold without cracking, even in plates up to */4 inch thick. Fabrication requires the making of either welded or riveted joints. The production of satisfactory welded joints of t h e straight chromium alloys has always presented considerable difficulty. Unfortunately, such alloys develop very coarse, crystalline structures when heated to near the melting point, their ductility and strength becoming thereby reduced. This is a natural characteristic, and apparently cannot be avoided by any process of welding, although the effect may be somewhat minimized by suitable heat treatment of the weld. However, for equipment not required to withstand severe shocks or strains, or for tanks subject to moderate pressures, welding properly done is entirely satisfactory. Either acetylene or arc welding may be used. The nickeliron-chromium alloys (Type 4) have a material advantage in this particular, as they have no tendency to air-hardening; and as the presence of nickel prevents excessive grain growth, the weld remains tough and ductile, and no particular skill on the part of the welder is required in producing it. Type 5, owing to the very high chromium content, is probably the most unsatisfactory for welding purposes; it will develop exceedingly coarse crystalline structure, which cannot be remedied by heat treatment, and welding, except on castings, should be avoided if possible. The problem of riveting joints has been successfully overcome. Notwithstanding the apparently low carbon content, of the stainless irons, they harden or become brittle when cooled in air from too high a temperature. This tendency is greater the lower the ratio of chromium to carbon content, as with Type 2. If rivet manufacture and rivet driving are not performed at proper temperatures, rivet heads show an astonishing and disconcerting tendency to fly off, even without the slightest provocation. I n Type 3, air-hardening tendencies exist to a very much less degree, and this tendency in the normal iron-chromium alloy is diminished by increase in silicon content up to a certain limit. If, however, manufacturing operations are properly controlled, and heating of rivets for driving is also controlled by not heating above 760" C. for Type 2, or 790' C. for Type 3, riveted joints will be fully as strong as though made from the usual structural steel. The difficulties encountered with straight chromium alloys are apparentIy non-existent with alloys of Type 4, which are free from air-hardening tendency and show little inclination to develop coarse crystalline structure. With small rivets ( 5 / ~ inch diameter or under) upsetting can be done cold, but the disadvantage remains of possible increased corrosive attack because of strains in the metal so introduced. For all equipment which must withstand high pressures, shocks, etc., riveted joints are preferable while if the equipment will be required to withstand high temperatures welded joints will be preferable, as rivets tend to loosen up under such conditions. Such shapes as channels, I beams, angles, etc., have been successfully produced for Type 2 and 3 analyses. The latter alloy, being the more workable, is better for such parts. Seamless drawn tubing is now being produced in a range of sizes up to 5 or 6 inches outside diameter. It is largely made from the Type 3 analysis, either with medium or high silicon. Welded tubing is also obtainable. When annealed and drawn to smaller sizes this shows excellent properties, the coarse, crystalline structure produced by welding being broken up by the mechanical working during the drawing operation. Either the usual threaded joint or the Van Stone
October, 1927
INDUSTRIAL AND ENGINEERING CHEMISTRY
joint may be used. The Van Stone joint is desirable if frequent taking down will be necessary, as the stainless irons tend to seize in threaded joints. Stainless iron tubing, because of its high oxidation resistance, is eminently suitable for construction of recuperators, heat exchangers, etc. The question of castings is an important one. Actually, all the types described above may be cast, but it is difficult to produce sound castings free from blowholes and porosities with the extremely low carbon of the stainless irons. The usual carbon content of stainless castings will run from 0.25 to 0.40 per cent; and obviously much higher carbon may be used when hardness is desirable, as for parts to resist wear and abrasion. With high carbon the alloys are really steels and require careful annealing before becoming machinable. Further,
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since the molten alloy is somewhat viscid and gummy, intricate castings with small sections are difficult to produce; also larger-sized castings, as may be made from steel, are still an impossibility. Probably the easiest cast and the most successful alloy for casting purposes is Type 5. Physical properties of such material (annealed) are given in Table I [Castings (a)].This is a moderately soft material, but has a low ductility. The Type 3 analysis, with 16-18 per cent chromium and 0.30 to 0.35 per cent carbon, has also been successfully cast, although it is slightly more difficult to obtain sound castings. Castings of this alloy have the advantage of greater toughness and strength. The physical properties of these castings are shown in Table I [Castings ( b ) ] .
Mothproofing Fabrics and Furs’ A Consideration of the Procedures That Have Been Proposed by Others and a Description of a New Process By Lloyd E. Jackson and Helen E. Wassell MELLON INSTITUTE OF INDUSTRIA&RESEARCH, UNIVSRSITY O F PITTSBURGH, PITTSBURGH, PA.
The authors have recently completed a comprehensive investigation of possible moth-repelling chemicals, in which the discovery was made that the cinchona alkaloids, as well as their derivatives, are particularly effective moth repellents. The fact that they can be prepared to be soluble in a wide variety of appropriate vehicles makes it possible to use some one or more of these substances under almost any condition encountered in the production and use of materials susceptible to moth attack. A process in which one of the cinchona alkaloids is employed has been in successful commercial use for more than a year in the dry-cleaning industry. Processes utilizing the cinchona alkaloids are adaptable to many other
industries in which the clothes-moth is a destructive nuisance. Products of the cinchona alkaloids have been shown to meet criteria of excellence heretofore unsatisfied by other moth repellents. They are inodorous; they adhere to the materials to which they are applied: they can be put on evenly like a dyestuff: they are not apparent on the materials treated; they do not dust off: they do not affect undesirably the physical properties of textile fibers; they can be made soluble in inexpensive organic solvents, such as petroleum naphtha, as well as in water: they are nontoxic to human beings: they are valuable clothes-moth repellents; and they are economical to use industrially.
...... . . ...... UCH has been written about the destructiveness of the clothes-moth, but only a rough estimate can be made of the damage caused by this common pest. Clothes-moths are continually engaged in their work of destruction in many parts of the world. There are, in fact, many records of their vast damage since the beginning of history, in writings concerning European, ilsiatic, African, and other countries. Dependable data on the losses caused by clothes-moths are unobtainable, because these insects do their destruction in so many different places, such as homes, mills, storehouses. stores, etc. The annual loss, in the United States alone, due to injurious insects of all kinds is conservatively placed a t two billion dollars.2 There is little doubt that millions of dollars of this loss are attributable to the clothes-moth. Many methods have been proposed for controlling clothesmoths. During the last fifty years more than forty patents have been issued in the United States on procedures of combating the pest. Various methods of control are mentioned in textbooks, government bulletins, trade journals, and household magazines.3 Many of these procedures have become
M
’
Received March 28, 1927. Fernald, “Applied Entomology,” p. 34. SSee, for example, Smith, “Our Insect Friends and Enemies,” p. 241; Packard, “A Guide to the Study of Insects,” p. 347; Cornstock, “Manual for Study of Insects,” p. 257; Hygeia, 3, 642 (1925); A m . Dyestuf Reptr., 14, 151 (1925); Bur. Chemistry, Farmers’ Bull. 1363; Texlzle Colorist, 48, 89 (1926). 2
common knowledge, and some of them are the bases of commercial products; but most of the methods are either ineffective or a t least inefficient in repelling clothes-moths. ’ Often the substances used to combat clothes-moths have some undesirable characteristic, such as malodor; or they affect adversely the physical properties of the materials treated. The use of most materials recommended for controlling clothesmoths depends upon the production of a vapor which is toxic or otherwise offensive to the insects. The clothes-moth readily adapts itself to its food. The presence of comparatively large quantities of any one or more of a large variety of chemicals in its natural food of wool or feathers does not curtail its voracious appetite. It is generally known that petroleum distillates, such as gasoline and naphtha, destroy clothes-moths. For this reason it has been a practice of the housewife to have moth-infested wearing apparel, furniture, and other household articles drycleaned to destroy clothes-moths in them. Such treatment exterminates the insects, but it does not prevent other clothesmoths from entering the materials later, to continue the destruction that was temporarily curbed. Early in 1921 a group of dry-cleaners and dyers, organized as the hlundatechnical Society of America, established a Multiple Industrial Fellowship in Mellon Institute of Industrial Research for the purpose of investigating problems pertaining to the garment-renovation industry. Because the inadequacy of dry-cleaning for clothes-moth control was
