Feb., 1915
T H E JOCTRNAL O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
99
THE COMPOSITION O F PAINT VAPORS
b y t h e mercuric chloride reaction. T h e iodine pentoxide method was also used for t h e quantitative determination. I n t h e application of both methods, however, I n this Journal’ a communication b y H. A . Gardner, a fundamental mistake was made in t h a t t h e a u t h o r of Washington, appears under t h e above title. T h e ignored t h e fact t h a t fuming sulfuric acid a n d formic communication purports t o describe a n experimental acid give rise t o carbon monoxide when t h e t w o are inquiry as t o ‘ I T h e composition of paint vapors,” brought together. This is surprising when i t is together with a s u m m a r y of results obtained, supple- pointed o u t t h a t t h e presence of formic acid in paint mented in some instances with a discussion of t h e d a t a . vapors is specifically s t a t e d b y Gardner as a result of I n t h e main, t h e results described therein can be t a k e n his own work (see conclusion 111). I t is, therefore, as confirmatory of already well-established a n d ac- t h e more surprising t h a t i n view of this knowledge cepted facts, a n d t h e present writer intends i n this he should have seen fit t o lead vapors known t o concommunication t o deal with only t w o statements, t a i n formic acid through fuming sulfuric acid in a n d t o offer detailed criticisms thereon: a n experiment designed t o detect t h e presence of carbon A-Concerning t h e presence of carbon monoxide monoxide. T h i s is sufficient t o render all t h e carbon in paint vapors. monoxide observations of Gardner wholly invalid, B-The observation as t o t h e change in weight of even from a qualitative point of view. T h e figures linseed oil a n d oil-pigment paints in t h e process of given for carbon monoxide have, however, some indrying. terest as confirming t h e s t a t e m e n t of Gardner as t o A-PRESESCE O P C A R B O N M O S O X I D E IK P A I K T V A P O R S t h e increased r a t e of formation of volatile products T h e conclusions arrived at b y Gardner are as follows: effected b y basic pigments; correctly expressed, t h e I-When linseed oil or similar drying oils are spread in thin results obtained show t h a t linseed oil alone, or in conlayers, the,absorption of oxygen which takes place is accom- t a c t with pigments, gives rise in drying t o volatile panied by the evolution of considerable amounts of carbon di- products, which products, when led through fuming oxide and organic substances. Carbon monoxide is also evolved sulfuric acid, yield carbon monoxide, and t h a t if it is in small amount. assumed t h a t t h e volatile products are of identical 11-Oil paints containing lead or zinc pigments do not emit composition n o m a t t e r what pigment is present, t h e n volatile compounds of a metallic nature. t h e increased r a t e of production of carbon monoxide 111-Drying paints evolve water-soluble acid substances such as formic acid, as well as acid substances which are apparently as described indicates a n increased r a t e of production of a fatty nature. Carbon dioxide and carbon monoxide are of volatile products b y t h e use of basic pigments. also present in the vapors from the drying paint. The type of T h e carbon dioxide determinations are open t o serious pigment used in the paint may directly affect the amount and criticism (see Section 8, p. IOO), a n d , therefore, n o decharacter of the volatile substances produced. Basic pigments ductions can be d r a w n therefrom. apparently stimulate the evolution of such products. Objection must also be made t o t h e experiment IV-Aldehydic substances are present in the vapors from (No. V I ) made t o determine t h e effect of turpentine, drying oil paints. These substances probably have a marked from t h e results of which it is inferred t h a t turpentine bactericidal effect upon pathogenic bacteria and would thus increased t h e q u a n t i t y of carbon monoxide produced. account for the sanitary value ascribed to oil-pigment paints. Here Gardner appears t o have entirely overlooked T h e reputed discovery of carbon monoxide in paint t h e f a c t t h a t formic acid is a product of t h e oxidation vapors, here s t a t e d , has become widely known, largely, of turpentine,’ so t h a t t h e increased production of t h r o u g h its incorporation i n a later publication2 carbon monoxide in his a p p a r a t u s necessarily follows b y t h a t author. This later publication has been refrom this cause. printed in E ~ r o p ea,n~d has received detailed consideraT h e present writer has a t t e m p t e d t o repeat t h e extion b y those interested in t h e problem of painters’ hygiene, which has been so acutely occupying t h e a t - periments of Gardner (making proper provision for tention of government committees of inquiry i n t h e removal of formic acid vapors), a n d i t appears t h a t a p a r t from t h e foregoing objections, certain other Europe. points of importance are brought t o light, of which On reading through t h e account of these experiments t h e present writer came t o t h e conclusion t h a t t h e ex- t h e following m a y be cited: I-The so-called paint used b y Gardner i n Experiperimental method adopted b y Gardner was open t o ments 11, 111, I\- a n d V contained 6 0 per cent pigment serious criticism, a n d t h a t t h e conclusions t o which h e h a d come were n o t supported b y a n y experimental a n d 40 per cent linseed oil. Such a mixture has no evidence he h a d brought forward. For t h e detection practical importance, a n d , therefore, t h e results ohof carbon monoxide t w o methods were used, nie., tained are correspondingly denuded in value. a-The duration of t h e experiments was so short t h e liberation of iodine from iodine pentoxide a t 130’ C. a n d t h e formation. of potassium formate b y t h e inter- t h a t t h e paints were not d r y at t h e end of t h e experiaction of carbon monoxide with heated solid potassium ment a n d , therefore, t h e results can he considered t o h y d r a t e with subsequent confirmation of t h e formate apply only t o t h e first 5 hours’ drying. 3-The s t a t e m e n t t h a t basic pigments apparently 1 TIXIS JOURNAL. 6 (1914), 91. 2 Bull. 41, published by the Scientific Sect. of Educational Bureau, stimulate t h e evolution of such products is only in Paint hlfrs. Assn. of U. S.,and read before Int. Assoc. Master House accordance with long-recognized facts, a n d in order Painters and Decorators of United States and Canada, Indianapolis, Ind., By C. A. KLEIN Received January 4, 1915
Feb. 2, 1914. 0 . & C . Trades Jocrrn.. 45 (1914), 1000.
1 Kingzett and Woodcock, J . Sac. Chem. Ind., 31 (1912), 2 6 5 ; 29 (1910). i 9 l .
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T H E JOURNAL OF INDC‘STRIAL A N D ENGINEERISG CHEMISTRY
t h a t t h e information obtained from such experiments should be of practical value, i t becomes necessary t o realize t h a t t h e function of basic pigments is t o stimulate drying. I n order t o render comparison possible, experiments should be made in u-hich paint is dried either t o complete dryness, or t h a t t h e well-known nondrying properties of certain pigments should be compensated for b y t h e addition of driers (as is done in practice) so t h a t paints drying a t t h e same r a t e should be compared; otherwise i t is impossible t o draw a n y conclusions on experiments extending over t h e same length of time. 4-It is t o be noted t h a t although great care was taken t h a t t h e air aspirated through t h e painted bottles should be free from carbon monoxide a n d carbon dioxide, no provisions appear t o have been made t h a t t h e painted bottle itself contained air of t h e same description. N o arrangement is shown for t h e removal of laboratory air from these vessels prior t o t h e addition of the paint, nor is a n y arrangement shown for t h e addition of t h e paint while t h e a p p a r a t u s is in use. 5-The r a t e of aspiration of air through t h e a p p a r a t u s is not stated, nor is t h e quantity of air passing through t h e a p p a r a t u s recorded. 6-The coating of stoppers with paraffin is a highly dangerous proceeding unless special precaution is t a k e n t o insulate such stoppers from heat. This a p plies more particularly t o t h e bottle prior t o Bottle 13, from h e a t radiated from Burner 14. h l y own experience bears out t h a t of Morgan a n d McWhorterl as t o t h e liberation of iodine from iodine pentoxide by gases which although normally without action became active when passed through tubes jointed in this manner. i-The a m o u n t of carbon monoxide is expressed as a percentage, b u t t h e basis on which this is expressed is not stated. T h e great delicacy of t h e iodine pentoxide method a n d t h e difficulty of exact determinations with this substance in dealing with quantities so low as those recorded in t h e paper. is well known t o all those who have worked with t h e material. I wish here t o place on record t h e fact t h a t in m y experience iodine pentoxide prepared most carefully b y t h e method of Scott a n d Archbuckle? appears t o undergo slight decomposition a t a temperature of 130’ C., such r a t e of decomposition gradually decreasing t o a constant figure, which must be determined separately for each set of conditions, a n d allowance must be made in calculating results. AIy experience in this connection is wholly confirmed b y t h a t of Dr. R . W. hlerriman, of Guy’s Hospital, London. I a m not in agreement with Gardner in his assumption t h a t fuming sulfuric acid is capable of destroying all organic vapors produced in t h e drying of paints which can liberate iodine from iodine pentoxide. T h e action of m a n y organic compounds on this reagent are well known, a n d in these circumstances t h e determination of carbon monoxide is most difficult. Indeed t h e a u t h o r himself evidently recognizes t h e possibility of “aldehydes” escaping absorption b y t h e fuming sul1 f
J . A m Chem S o c , 29 (1907), 1589. J . Chem. Sos , 1901, p 302.
Val.
j ,
NO, 2
furic acid for in Experiment 1- (repeated), using K O H as detector, he specifically introduces a wash bottle of alkaline bisulfite “ t o collect a n y traces of aldehydes which, if evolved b y t h e paints, might possibly escape absorption by t h e sulfuric acid.” Aldehydes h a d previously been detected b y him (see conclusion I V ) . No recognition of this observation appears t o have been made in the iodine pentoxide determinations although t h e effect of aldehydes on t h e values obtained is t o o serious t o be ignored. The exact method of determination is not specified though b y inference i t is t o be concluded t h a t t h e iodine released was titrated. I n this connection t h e reference on line 28, page 94, t o t h e determination of carbon monoxide is evidently a mistake a n d ought t o read ”carbon dioxide.” 8-The figures quoted b y Gardner as showing t h e q u a n t i t y of carbon dioxide produced during t h e j hours’ drying of oil or paint are open t o serious objection from a n analytical standpoint. I n t h e first place, Fig. I1 shows a wash bottle containing distilled water ( N o . 9) through which t h e gases containing carbon dioxide were passed, prior t o entering Bottles 1-13, which contained barium hydrate for t h e purpose of absorption. The solvent action of distilled water on carbon dioxide has surely been overlooked in this case, so t h a t a n y figures obtained b y titration of t h e barium hydrate solution in these circumstances must be of questionable value. I t is noteworthy in this connection t h a t in Experiment 111, where quite similar conditions prevailed, t h e a u t h o r recognized t h e possibility of solution of carbon dioxide in water through which these vapors were l e d ; indeed he records, page 93, line 43, t h a t “ T h e presence of carbon dioxide in t h e water m a y partially account for t h e acidity’’ of water so treated. Further, i t appears t h a t t h e use of fuming sulfuric acid (in Bottle S), through which t h e volatile products are led prior t o t h e determination of C O a n d CO:! is a dangerous proceeding, a n d t h e effect of formic acid has already been pointed o u t , b u t it is also evident, hotvever, t h a t t h e well-known production of sulfur dioxide b y t h e action of organic compounds on sulfuric acid has been ignored. N o provision (other t h a n a single mash bottle) mas made for the removal of this gas, a n d no indication is given t h a t t h e possible effect of this gas on t h e barium hydrate solution is recorded. I t is t h e experience of t h e w i t e r (working on t h e lines of Gardner) t h a t further complication takes place, owing t o t h e production of a white mist of sulfuric anhydride when gases are led through fuming sulfuric acid. This mist i t is impossible t o absorb completely in water, a n d t h e writer has invariably found t h a t i t traveled through m a n y such washing bottles with only partial absorption. Washing in a single bottle of water is wholly ineffective, with the result t h a t t h e precipitate obtained in t h e barium hydrate bottle contained barium sulfate, so t h a t direct t i t r a tion of t h e barium hydrate after t h e experiment is of no value. T h e production of carbon dioxide during t h e drying of linseed oils or paints containing this oil is not disputed, b u t t h e qualitative figures contained in t h e communication in question are open t o serious
Feb., 1915
T H E JOURNAL OF INDUSTRIAL A N D EXGINEERING CHEMISTRY
IO1
criticism. T h e qualitative detection noted i n Experiments I a n d I1 is n o t open t o this foregoing objection, because in this case only 6 6 ” sulfuric acid was used, a n d t h e effects produced b y fuming sulfuric acid were absent. 9--The effect of light in t h e drying process has evidently not been fully appreciated b y t h e author, inasmuch as apparently in all t h e experiments t h e oils or paints were enclosed in such a manner as t o partially or wholly exclude light. Such conditions h a r e no industrial parallel, a n d t h e utility of t h e investigations is thereby vitiated. F r o m a scientific standpoint t h e omission is i m p o r t a n t , i t being a well-established fact t h a t drying is seriously impaired b y t h e absence of light. I n view of t h e foregoing criticisms, it I S submitted t h a t no single piece of evidence has been brought forward which can justify t h e assertion t h a t carbon monoxide has been or can be detected in paint vapors. I n concluding t h e criticism of this portion of t h e work, t h e present writer desires t o make it clear t h a t his criticisms are offered in n o carping spirit. It has become necessary t o definitely record such criticisms in view of t h e publicity given t o t h e results under discussion, a n d t h e possible influence of such s t a t e ments as have been based on these results, in so f a r as t h e y concern t h e hygiene of t h e painters’ trade. Wide a n d extensive publicity h a s been given t o t h e carbon monoxide theory of Gardner, not only in England, b u t on t h e Continent, a n d i t has appeared undesirable t h a t such conclusions should in their present s t a t e go unchallenged. It is a m a t t e r of regret t h a t t h e a u t h o r should have seen fit t o publish the results of a n obviously imperfect investigation, in view of t h e i m p o r t a n t issues concerned. S t a t e m e n t s such as those contained in t h e publication already referred t o readily gain credence in certain quarters, irrespective of scientific accuracy, a n d although t h e a u t h o r explicitly s t a t e d t h a t “ t e s t s extending over a greater period should be made t o substantiate t h e figures presented,” this reservation has n o t prevented t h e publication of his conclusions in t h e technical a n d public press of Europe, because in his later publications no such reservation appears; in point of fact t h e discovery of carbon monoxide in t h e vapors from drying oils a n d paints is positively asserted a n d i t is s t a t e d t h a t some of t h e s y m p t o m s of poisoning observed among painters previously ascribed t o other causes can be more probably explained b y t h e presence of this gas. T h e experiments, interesting as t h e y m a y be, cannot be regarded as strictly conforming t o t h a t rigid accuracy necessary for t h e substantiation of t h e evidence t h e y p u r p o r t t o reveal. There is n o evidence t h a t paint vapors contain carbon monoxide.
the tests, are interesting. They may be partially accounted for by assuming that the amount of air passed through the tanks in 48 hours was very small. It will be well a t this point to discuss the experiments on linseed and oil-pigment paints, as made by Sabin. He describes a series of tests in which various paints were applied to small glass plates, the increase in weight shown by the paints being recorded at different periods. At the end of 7 days, raw linseed oil showed a gain in weight of 18 per cent, while white lead paint showed a gain of approximately 1 5 per cent. “The writer carried out a similar series of tests with a set of paints made up with 60 per cent of pigment and 40 per cent of raw linseed oil. The gain in weight of the films a t the end of 7 days was as follows :
I N WEIGHT O B S E R V E D D U R I N G T H E D R Y I N G
F r o m this comparison i t is evident t h a t no serious differences exist between t h e results of these workers, a n d there is no ground for t h e suggestion t h a t t h e later results bring t o light a n y new feature. T h e observations of Sabin a n d Gardner as above shown are similar t o those observed b y m a n y other workers, a n d have limited interest, because of their limited range.
B-CHAh-GES
O F LIXSEED
OIL AKD LINSEED
OIL PAINTS
Gardner has investigated t h e change i n weight observed in t h e drying linseed oil of paints, a n d in his general discussion of t h e results obtained f r o m such inquiry s t a t e s : “The results obtained in Experiment 11, in which the paint films showed but slight if any increase in weight a t the end of
Per cent Linseed oil. . . . . . . . . . . . . . . . . . . . 14.0 Corroded white l e a d . . , , . , , . , , , , 6 . 4 7.1 Sublimed white lead. Zinc oxide.. , , , , . , , , , . , , , , . , , , , 5 . 4 Lithopone.. . . . . . . . . . . . . . . . . . . . 5 . 5
“These tests indicate that oil-pigment paints do not gain in weight to the same extent as raw linseed oil. Heretofore, however, investigators have not given consideration to the pos’sibility that pigments may stimulate not only those processes which cause the oil to increase in weight through the absorption of oxygen, but also those processes and reactions which cause the oil to eliminate volatile substances, which might detract materially from the weight of the paint. In this connection it is of interest to cite the tests of Olsen and Rather upon the drying of linseed oil. They record a gain in weight of 18 per cent a t the end of approximately I O weeks. They also showed the elimination of approximately 5 per cent of carbon dioxide and 15 per cent of water.” Before discussing in detail t h e points raised b y t h e a u t h o r on this subject, i t is necessary first t o make some observations with reference t o t h e film tests detailed above. T h e disparity between t h e results of Gardner a n d Sabin is not so great as would appear a t first sight, because t h e figures as presented are not comparable. T h e results of Sabin are calculated on t h e oil used; indeed, this is expressly stated in t h e original communication of Sabin:’ “In constructing t h e curves of drying, only t h e oil is t a k e n into account, a n d t h e curves show t h e percentage gain or loss of t h e oil as if n o pigment were present; t h a t is, t h e pigment is assumed t o be inactive in all cases.’’ I n order t o compare t h e results obtained by these t w o workers, i t is only necessary t o express their results on t h e same basis. T h e most convenient is t h a t adopted by Sabin, v i s . , increase of weight expressed on linseed oil content of t h e paint. Gardner used a paint containing 6 0 per cent pigment a n d 40 per cent linseed oil, so t h a t , calculating t h e results on t h e same basis, t h e comparison is as below: P E R CEKT GAIN I N \vEIGHi’
IK 7 DAYS Linseed o i l . , . . . . . . . . . . . . Corroded white l e a d . , , . , . Sublimed white lead, , , , , , Zinc oxide.. . . . . . . . . . . . . . . . . . . . . . . . . . . . Lithopone . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
THISJOCRNAL, 3 (1911), 2.
Gardner 14.0 16.0 17.5
Sabin 18.0 15.0
13,s
16.0
14.75
....
....
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
T h e observations of Sabin, as described in t h e original communication, are, however, much more comprehensive a n d consist essentially in t h e determination of changes in weight which t a k e place over a lengthy period of exposure of oil a n d paint films (up t o 8 months). As such, t h e y have a n enhanced value. In brief, t h e y show t h a t paint films increase in weight t o a maximum value, a n d t h e n slowly decrease, a n d t h a t even after a period of 8 months t h e decrease contipues. R a w linseed oil shows t h e same behavior b u t decreases in weight more rapidly t h a n does t h e oil cont e n t of a n oil paint. Similar observations were made b y t h e Chemical S u b - c o m m i t t e e of t h e Netherlands White Lead Commission, appointed in 1903. These results have certain practical bearings in particular a s showing t h a t t h e oil portion of paints undergoes a slow b u t continuous decomposition on exposure t o air. According t o Sabin, in 2 4 days, films of paints containing Whiting, T e r r a Alba, Silica, Asbestine, Barytes, China Clay, White Lead, or White Zinc show increases in weight of between a b o u t 1 2 a n d 13 per cent, having fallen from maximum values of from 1 3 t o 16 per cent. T h e following table from t h e report of t h e Netherlands Commission shows t h e changes in weight (decreases) in percentages expressed on t h e original layer of d r y paint. Mica plates covered with paint were placed o u t of doors after having become dry. NAME O F P A I N T 20 Whitelead.. . . . . . . . 2 . 8 Zinc white. . . . . . . . . . 2 . 9 Lithopone. . . . . . . . . . .
Duration of Exposure in Days 40 60 80 120 200 4.0 4.1 2 1. 2 . . 8.6 35.8 60.8
. . . . . . . . . . . ... . . ..
230
.. .. .. .. .. .. .. .. 83.9
These results show t h a t white lead paint loses much less o n exposure t o t h e air t h a n zinc white or lithopone, a n d constitute a striking refutation of t h e last sentence of t h e following s t a t e m e n t : “Oxide of zinc is practically without action on linseed oil; therefore, when it is ground in that medium the conditions that obtain cannot be compared with those that exist in the case of white lead. The drying of paint made from oxide of zinc is due entirely t o the siccative nature of the oil itself in which the oxide of zinc may be considered as mechanically suspended. We have here a state of things more readily under control than is the case with white lead paints in which the powerful siccative action of the hydrate portion of the white lead often proceeds too far. The oil is then burnt up so to speak; the paint perishes and ‘chalking’ results.”1 This a n d similar s t a t e m e n t s are used t o decry t h e properties of white lead b y those whose interests lie in t h e sale of other pigments. It is a n open question whether t h e behavior of paint films can be correctly studied b y t h e use of linseed oil a n d pigment alone. I n general, turpentine or a similar volatile thinner is present in paint when technically applied, a n d there is good reason t o believe t h a t such thinners may not be without effect in determining t h e character of t h e oxidation processes, more particularly in so far as t h e volatile products are involved. T h e whole problem of t h e drying of linseed oil alone or when used as a paint medium is one of extreme difficulty, a n d a t t h e present time such information as 1 From advertisement, page 498, “White Paints and Painting Materials,’’ Scott, pub, by T h e Modern Painfer, Chicago, 1910, and attributed t o J. Cruickshank Smith in a lecture before the Institute of British Decorators.
Vol. 7 , No.
2
is available appears t o be so lacking in agreement, a n d so contradictory, t h a t no t r u e explanation of t h e chemical changes has yet been brought forward, although m a n y theories have been published. T h e formation of volatile products (other t h a n carbon dioxide a n d water) during t h e drying of linseed oil has been known f o r some time, a n d more recently t h e hygienic value of these products has been appreciated. The presence of t h e lower f a t t y acids, aldehydes, etc., has been demonstrated, b u t as yet no detailed examination of t h e products has been carried o u t . This is a problem which few technical chemists have t h e facilities for attacking, a n d t h e y might well engage chemists more conveniently placed who have liquid air a t their disposal. By such condensation a n d collection of these volatile products a t low temperatures a n d their subsequent examination it is highly probable t h a t valuable evidence as t o their chemical constitution would be obtained. T h e course a n d t y p e of oxidation is apparently influenced b y t h e t e m p e r a t u r e a n d this has i m p o r t a n t practical application. T h e great disparity between t h e figures given for increase of weight of films b y different workers indicates t h e difficult nature of t h e inquiry. T h e so-called ( I oxygen absorption values” a s determined b y t h e exposure of films t o air, on open plates or t h e like, cannot claim t o be anything more t h a n empirical values, a n d have a correspondingly reduced scientific interest. I n such methods there is absolute disregard of t h e formation of volatile products, a n d t h e values obtained in no way represent t h e “ t r u e oxygen absorption.’’ T h e investigators who h a v e a t t e m p t e d t o determine t h e t r u e oxygen value have realized t h e complicated character of t h e volatile products, b u t have in nearly every case considered t h a t passage through calcium chloride a n d potash would be sufficient for their retention-a quite unjustifiable assumption in our present state of ignorance a s t o t h e t r u e chemical character of t h e volatile products. These a n d m a n y other problems present themselves in t h e detailed s t u d y of paint, a n d there is a wide field for t h e scientific investigation of t h e chemical changes involved in t h e application a n d use of paints. CHEMICALLABORATORY OF THE BRIMSDOWN LEAD CO.. LTD ENPIELD HIGHWAY,MIDDLESEX,ENGLAND
A STUDY OF VAFUOUS TESTS UPON GLUE, PARTICULARLY THE TENSILE STRENGTH’ By AucusTus H. GILL Received Sovember 17, 1914
T h e object of this work was t o compare t h e various tests applied t o determine t h e properties of glue a n d more particularly t o see if t h e y bore a n y relation t o its tensile strength. I-PRELIMIKARY~
TEST-FOllOWing t h e work of F e l ~ ,t h~e viscosity of I j per cent solutions of glue a t 30’ C. were determined with t h e Engler viscosimeter; as t h e VISCOSITY
1 The experimental work of this paper was done b y six students, working successively. Each worker’s name is given in connection with the report of his experiments. 2 By W. A. Marshall. a Chem. Zetf., 21, 56, 70.
