July, 1932
I N D U S T R I A L -4N D E N G I N E E R I N G C H E hf I S T A Y
When I \\rote that letter in June, 1930, I did not know that anyone n-as contemplating recommending the intramuscular injection of ethylene glycol. I had in mind only the proposed use of the compound in food and beverage products, a matter to which Hanzlik states that he has not given special consideration, The chief reason why the letter was not published earlier seems to have been because some who had contemplated using the glycol in food products promptly abandoned the plan when told of my results. Pressure of other work and rather prolonged visits abroad prevented my carrying the work as far as was desirable. It would be very important, for example, to have more information as to exactly what happens to the compound in the body. It seems to be largely destroyed. It has been definitely shown that it is not converted into glycogen, in this respect differing markedly from propylene glycol which has been found by Salter here to form glycogen and so to have true food value. One of the questions which arujes in connection with ethylene glycol is whether there may not be formed toxic intermediary products. There seems to be evidence that in the case of methanol, formaldehyde is produced as an intermediary product. It may be that the toxic action of the glycol is due to such intermediary products rather than to the comparatively small amount of oxalates which appear in the urine. The extraordinary contrast between the toxicity of ethylene and propylene glycol suggests that in the case-of the former some toxic product is formed which is later destroyed or has not been detected. In this connection I may remark that my observations of the effect of the glycol upon the kidney were somewhat more disquieting than were those of Hanzlik. The kidneys of rats which had received for 15 days doses of ethylene glycol which had not checked the growth or produced obvious symptoms of any kind, were described by Tyzzer as follows: “Macroscopically the kidneys were mottled as though sprinkled with fine sand; microscopically, sections presented the following appearance: There is extensive loss of parenchyma, the convoluted tubules being reduced to small areas. The cortex is thus largely replaced with connective tissue and the remaining tubules are distended. There are widespread accumulations of crystals of various types and a considerable number of the tubules are filled with polynuclear leucocytes.” Hanzlik found that the drinking by rats of a L per cent solution of glycol caused distinct pathological change3 in the kidneys. But he argues that the “equivalent for a 70-kg. adult would be about 154 grams (more than a quarter of a pound) taken for about 6 or 7 years.” It is interesting to recall what actually happened to Hansen’s patients who took a single dose of about 100 cc. of the glycol; the quantity mentioned by Hanzlik would probably kill more than 2000 persons. I desire to repeat, however, that although protests have been made to such use, I see no objections to the addition of the glycol to the antisyphilitic remedy, but the people should be protected against the promiscuous use of the compound in food products. Vastly more poisonous substances (strychnine, for example) are in conshant use by physicians, but this does not justify the addition of strychnine t o a great variety of patent medicines and even to beverages (as has occurred in the past). The trouble is that there are too many totally incompetent individuals dabbling in this field, as was well illustrated by the appalling results in the “ginger paralysis” episode. . REIDHUNT
837
Dilatometric Measurement of Hydration Editor of Industrial and Enginem‘ng Chemistry: I n a recent paper [IND.ENQ.CHEW,23, 1298 (1931)] Gustavson has criticized the improved dilatometric method of measuring the potential hydration capacity of proteins in general, and of gelatin and animal skin in particular. Gustavson, in his comprehensive criticism of our hydration work, maintains that our measurements bear no relation to the actual hydration of the proteins. He bases his contentions, at least to some extent, upon work done by other workers sometime after the papers in question were turned over to the publishers of our work. Gustavson’s criticisms are apparently directed toward the effect of hydrogen-ion concentration upon what we have been pleased to cell ‘‘relative hydration.” I n the light of Gustavson’s comments, let us consider the mechanism occurring when isoelectric gelatin is placed in a solution of hydrochloric acid having a p H value of 4.7. Considerable swelling of the gelatin occurs. This swelling taking place a t the isoelectric point cannot be attributed to any osmotic effects and cannot therefore be explained by the Donnan membrane equilibrium theory, as outlined by Procter and Wilson and by Loeb. If the change in volume of this isoelectric system (gelatin-solution) is considered, it is found that a net contraction occum, and such contraction cannot be explained in the light of the Zwitterionic theory:
+
Gelatin H+ Gelatin cation
+gelatin cation
+ O H - 4gelatin + Hz0
since for this explanation we have assumed isoelectric gelatin in a hydrochloric acid solution a t pH 4.7 (isoelectric point of the gelatin). I n this isoelectric system, none of the ionic reactions (outlined above) given by Gustavson can take place, and here the net contraction of the system must be attributed to the adsorption and compression of water molecules by the hydrophilic substance-gelatin, Likewise, the swelling or increase in the volume of the gelatin itself must be due to this addition of water molecules or hydration, as distinguished from osmotic swelling in which the water is considered mechanically held. This fundamental idea upon which our studies of hydration (decrease in net volume of system) are based seems to have escaped our critic. The reactions which are proposed cannot explain R net contraction of the system, but only an expansion. When the gelatin i s hydrated in an isoelectric solution and is then transferred t o a more acid or more alkaline solution, a net expansion in volume does occur which we attributed to decreased hydration, but this net expansion in volume may be interpreted in terms of the reactions which Gustavson presents. Our measurements certainly show, under these conditions, the relesise of water molecules indicated by the increase in volume of the system. It may be held that these reactions result in the production and elimination of vater molecwles, which is in the strict sense of the word, dehydration. Although we did not attempt to explain why gelatin is less hydrated on either side of the isoelectric point, the obvious inference is that the effect must be due to the combination of the gelatin with H + and OH- ions as the case may be. This inference is not contrary to the contentions of Gustavson. However, as we pointed out in the article on HARVARD M E D I C SCEOOL ~L gelatin, these effects are completely reversible, and the curve, as BOSTON, MABS. shown in that article, may be obtained either by hydration of dry April 4, 1933 gelatin or by dehydration of the completely hydrated isoelectric gelatin. Such behavior of the system suggests an adsorption equilibrium rather than a definite chemical reaction. GUIDAALLA ANALIBICHIMICA DELLE MERCICON SPECIALE RIQUARDO A L DAZIDOQANALI DEL REQNO D’ITALIA PER LA PRECISA DICHIARAZIONE A further point which in our minds seems particularly incompatible with Gustavson’s explanation of our work (and which E TASSAZIONE DI PRODOTTI GREQQIE LAVORATI. Luigi Settimj. 338 pages. Ulrico Hoepli. Milan, Italy. Prioe, 40 lire. has been overlooked by him) is the influence of temperature upon
838
INDUSTRIAL AND ENGINEERING CHEMISTRY
the volume change. In the articles on gelatin and animal skin, it was shown that when the measurements of this net contraction of the systems were made a t different temperatures an increased contraction results a t the lower temperatures. This is what one should expect if dealing with an adsorption phenomenon, but, if the volume change were attributed to chemical action only (as the Zwitter-ionic concept postulates), the volume change of the system should have been the same for all of the temperatures used as the same p H value obtained a t equilibrium in every case. I n the case of the volume change for animal skin, the net contraction at 37.5’ C. was only 10 per cent of that a t 0 ” C., which would indicate that forces other than primary chemical ones play a role in our measurements. At pH values less than 3.5, it has already been pointed out by us that “at higher concentration of acid, effects other than hydration become important,” and again, “at the higher concentrations of acid, chemical changes may take place” [IND. ENG. CHEM., 22, 68 (1930) 1. Gortner, in his classical work on vegetable proteins, has demonstrated the presence of bound and free water and has shown that these play an important role in the life cycle of winter wheat. I n this work, he has shown that lower temperatures favor an increase in the so-called “bound water”-this bound water in our minds being practically what we have been pleased t o call “hydration.” I n a former paper we have postulated, “The water of hydration that exists in animal skin a t any process period can be compared to water bound by the tissue (and this binding of water in this state cannot be explained by the second law of thermodynamics). Animal skin in the fresh state contains both bound and free water in equilibrium bound water z*free water. During processing this equilibrium is altered, usually in favor of the bound water. The binding of water in the soak water can be changed about by the action of various chemicals, etc.” [ J .Am. Leather Chem. ASSOC., 26, 360 (1930)l. I n summation, we would state again that hydration as measured by us (net contraction of the entire system) is different from the forces set up during swelling. In the first place, there are those forces of chemical attraction between the molecules of water and certain of the groups of the protein. I n the case of gelatin, these forces cause the solution of the gelatin in water when the forces of cohesion between the gelatin molecules forming the gel can be overcome. The take-up of water a t the isoelectric point is in our minds primarily due to residual valency forces and in no way connected with direct chemical reaction such aa the Zwitter-ionic concept. At other points, on the acid or alkaline side of the isoelectric point, these forces which evidence themselves at the isoelectric point are undoubtedly present and active and must be responsible a t least to some degree for the water bound at other than the isoelectric point. A t other than the isoelectric point of the protein, it is entirely possible that our results can be interpreted to some degree by the Zwitter-ionic concept, but not entirely so in view of the many changes in protein structure which may take place in solutions of acids or alkalies. EDWINR. THEIS HARVEY A. NEVILLE LEHIQH UNIVERBITY PA. BETHLEHEM, January 29, 1932
,. .... .... Editor of Industrial and Engineering Chemistry: I n the paper on “Dilatometric Measurement of Protein Hydration” [IND.ENG.CHEW,23, 1298 (1931) ], I pointed out that the dilatation of the total volume of a fully hydrated protein system in an electro-neutral state, which is observed upon the addition
Vol. 24, No. 7
of acids and alkalies, is quantitatively accounted for by the removal of the highly hydrated H and OH-ions from the system by their combination with the amphoteric-ionic proteins. The independence of protein hydration from its degree of ionizationi. e., the p H values of the medium-has been amply demonstrated by means of widely different technics by Sorensen, Meyerhof, Weber, and others in contributions appearing years before Theis’s experimental work was initiated. But these workers’ testimonials are evidently a terra incognita to Theis. Recently, in an investigation by Weber and Versmold [Biochem. Z., 234, 62 (1931) ] utilizing Polanyi’s “nonsolvent space” technic in a modified form, the hydration of egg albumen is shown to be the same within such a wide pH range as from 3.1 to 10.3. How is it possible in light of these overwhelming evidences still to maintain that the volume change in the pH range from 2 to 9 is a measure of the degree of hydration of the protein? The contention of Theis and Neville that an adsorption process is indicated by the fact that their “hydration” curve may be obtained either by hydration of dry gelatin or by dehydration of the fully hydrated electro-neutral gelatin, only demonstrates an extraordinary lack of familiarity with the amphoteric-ionic concept. Their statement has no basis in fact as a proof of an adsorption process and a demonstration of the inapplicability of the Zwitter-ionic concept upon the reactions taking place in the p H range from 2 to 9. The present author never objected to the use of total volume measurements as a relative indicator of the degree of hydration of watersoluble proteins, as that of gelatin, in systems with constant H-ion concentration. But even in the latter instance an uncritical extension of the dilatometric technic to such heterogeneous systems as those of rawhide, with hair and impurities present, is doomed to be a failure. The reader is referred to a discussion of this phase of the problem in the chapter on “Leather” in the forthcoming Volume VI of ‘IAnnual Survey of American Chemistry.” Theis’s data of the pH factor in the hydration of gelatin, with the resulting unwarranted conclusions of a maximum degree of hydration of the gelatin in its isoelectric state, are untenable. His measurements have nothing whatsoever to do with the actual hydration of the protein in systems in which the condition of a constant pH is not fulfilled. It is evident that the main object of Theis’s investigations is to establish the changes in the “hydration” of hide proteins taking place in shifting the “neutral” hide substance to acidic or alkaline media, as in the work processes of pickling, liming, and chrome tanning. Furthermore, even the fixation of oils and soaps from fat emulsions is measured by the very same, evidently very versatile technic, but a change in nomenclature is introduced-i. e., ‘toilation.” Theis has collected an enormous amount of data and hydration curves of apparently very uncontrollabIe behavior, which, in fact, only show the vicissitude of H + and OH- ions on their reactivity with the hide. Their behavior is very simple when compared to basic chromic salts containing highly hydrated complexes and to oil emulsions, which are all “explained” by a radical simplification of problems. The question of the difierent temperature functions of the swelling and hydration processes has no bearing upon the problem under discussion. It may be said, however, that it is a wellknown story. Stiasny and Meunier, among others, have repeatedly emphasized this fact, but their statements evidently have escaped Theis’s attention What the authors have to say about the reactivity of Zwitter ions in the isoelectric zone makes any discussion of this question futile. +
K;H. GUSTAVBON ~ R E B R O ,SWEDEN
March 25, 1932
JUl\, lYJ2
1 A 1) I, 5‘1 I{ 1 A I, A
N D E N G I N E E H I N G C I i E M 1 S T 1%1
a39
Corrosion of Metals by Milk
Editor of Induslrial and Engineering Clternislry: The arrangement with rotating specimens is, in general, nut h W l o ~of Induslriol a& Enginewing Chemistry: more satisfactory in the United States than in Germany. This .9paper on “Corrosion of Metals by Milk” [IYu. Euo. CKEM., is also pointed out in OUT paper in the second paragraph on page 341 where we say: “Because of the uncertainty in regard to ve24, 339 (1932)] deais with the effects of opernting conditions on the behavior of nickel, copper, and some alloys. The corrosion locity and agration in the above experiments, another experimental procedure was tried.” We then proofed t o describe our of milk a t different rates of sow was studied; for this purpose, tests were made with FL rotating spindle machine, the specimens continuous flow method which we belicve is much more satisbeing suspended in stirrups attached to the moving arm of the factory than the method describ-d by Goldbach. The rotating spindle experiments were included in our paper appar;utus. I n Germany, howevor, we consider an arrangement like this only because they represent a condition which may sometimes he riot quite reliable. For, if the specimens Bse moved, m is done found in a plant, and also hecause we m r e rather surprised t o in the above-mentioned investigation, a state may he reached find that reproducible results could be obtained by such a crude when the attacking agent is moving wit.11 nearly the same ve- and simple method of adjusting velocitieu, Goldbach’s note regarding weight loss determination us. visual locity as the specimens thernselvrs. In order to avoid this unu the change in weight does not certaintr. we keep the suecimens still. and :&ate the solution examination is correct in so far t
used. The specimens we fastened to a cage, the BOIUtion being moved by a stirrer. The daba derived f r o m such stirring tests give results in good ticcord with practical experience. F i g u r e 2 of the above paper, repres e n t i n g the effect of velocity on c o r m sion, shows 5 emvc which i n c r e a s e s slightly from 20 to 1 3 0 meters p e r m i n u t e , hut then drops. The use of the r o t a t i n g machine perhaps affords an explanat i o n f o r t h i s behavior. At a veSTIRRING APPARATUS locity of 20 to 130 meterj mer minute the specimens are rotating in a quiescent solution; with inereasing velocity, however, tbe agent itself hegins to move, thus lowering the velocity of the specimens. In evaluating the results, the authors of the paper tnok only the change of weight into consideration. According to our experiments, the judgment of the corrodibility based only on the change in weight does not always suffice. It may he sufficiont with even attack, hut in case of pitting8 and, above all, of intergranular deterioration the rate of corrosion cannot be calculated from these data. They should be supplemented by investigations of structure and physical properties of the specimens before and after the corrosion t&. Fm%herdetsils about corrosion tests in Germany may be found in the tentative standards elaborated by the German Reichsawschuss for Metallsohuta, translations of which hsve already been published in English and Ameriean journuh [ M e l d Progress, 20, No. 4,91 (1931); Ind. Chemisl, 7 (80), 379 (1931); Aireraif Eng. (Lrmdon),3, No. 30, 195 (1931)l. GEORGG o m m m Dsamcan VERSUCHBANBTLLT SOLI L o m r * s m n. Bmnux-Ao~snsnos,G S ~ M I N ~ .April 28. 1832
.. . . . . . . ,.
Y.
would have complicated the paper tremendously without contributing anything to bring out, the point of the effects of operating conditions on corrosion in variaus parts of pasteurizing equipment. It would have shown numerous small pits with high currovion retos of nickel, no pitting a t loiv Corrosion rates of nickel, and no pitting with any of the other metals tested. Othor changes in structure and physical properties were nut investigated, &s they could hardly be expected in such short test8 as ours. In spite of the fact that the pitting wm of no particular importance, a note should possibly have been added to explain this, and we are grateful for this occasion to do so. E. A. TREBLEK N ~ ~ i o n rD f in r ~ rI’nonucia Conrona.rrov. isc.
B o m ~ o n Mo. ~.
Mar 14. 1832
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?‘lie Yellowing of Oils Owing to an unfortunste misunderstanding, Morrell and Marks, in condensing their original manuscript criticizing Elm’s puhlications on the above subject, changed the sense of their criticism materially by omitting a numher of essential points t o whioh reference iY made in Elm’s reply, printed a t the same time [INn. ENQ.CKEY.,24, 593 (1932)j. Elm’s reply, however, was printed in its original farm. This explains fully the apparent lack nf connection between these two notes. A. C. ELM Ter Nsw Jsnsrr Ziac C o . PA,,,,N, P*. May 25. 1932
Hydrolysis of Starch by Carbonic Acid In commenting OQ the article by M. A. Dewey nnd N.W. &me [Inn. ENQ.CKEY.,23, 1436 (l93l)l, it should be said that the saccharification of strtrcli by csrbonie acid under pmmue has some advantages over the usual hydrolysis by hydrochloric acid. A puretasting liquid is obtained; and the removal of the salts, obtained in the neutralization process, is avoided a t the plant. On the other hand, however, the equipment is larger and the reaction lasts longer. In both methods it seems that the deeoloratiun and subsequent filtration are not to be avoided. The method is, moreover, not entirely new, for in 1877 Bachet and Sitvalle, and in 1883Jacoh W. Decastro applied for patents. In the meantime, no practical application of these protected methods has been reported. A. P. 8CHULZ F o n s c m n o a n s s ~ ~riin ~ r Sria~m%aex~r&no.* S*awnmm= 13. B ~ n ~ rN65, w Qrrarmr April 13, 1832
