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T H E J O U R N A L OF I Y D U S T R I A L A N D ENGIiVEERING C H E M I S T R Y
Fortunately, i t seems as if such a n institution is already available a n d t h a t we may hope before long t o find new hands prepared t o t a k e up t h e responsibility f o r t h e execution of scientific research, as t h e universities may find it necessary t o be relieved of it. F o r many years the greatest gainers by t h e direct progress of scientific knowledge have been t h e manufacturing industries, a n d ever since their start they have been coquetting with the idea of advancing scientific progqess directly, a n d of turning i t into those directions which seem t o be of immediate advantage t o themselves, When research laboratories were first started b y industrial corporations t h e men employed in t h e m were expected t o confine their attention very strictly t o t h e immediate requirements of t h e industry with which t h e y were associated, a n d general investigation even of t h e general theory of t h e industry itself was discouraged, while publication of original work done in such a laboratory was regarded as almost o u t of t h e question. Wider experience. however, has shown t h a t t h e more general t h e work done b y the research laboratory, t h e greater are t h e results reaped b y the industry likely t o be, while t h e advantage t o t h e worker of being allowed t o publish a n y results of general, as opposed t o technical, interest, has become so obvious t h a t all t h e more i m p o r t a n t laboratories permit free publication of scientific papers. It seems likely t h a t t h e proportion of purely scientific work done in t h e research laboratories will increase rapidly as the advantages of such fundamental theoretical work t o industry become better known, a n d it would not seem too much t o hope t h a t before long t h e industries will devote themselves t o scientific research with a definite enthusiasm a n d energy which must make t h e m t h e predominant factors in t h e production of new knowledge. So t h a t it would appear t h a t i t is t o t h e industrial research laboratories t h a t we must look in the future for progress in all branches of science which are affiliated in a n y way with manufacturing industries. Organic chemistry has for some years been advanced largely through t h e work of men associated with industrial corporations; analytical chemistry shows every sign of following in t h e same path, while t h e other branches of chemical research are so closely associated with industry t h a t t h e y will be adequately provided for in t h e immediate future. I n physics, electricity
I
a n d optics are already directly associated with large a n d important industries maintaining adequate research laboratories, a n d t h e other branches of physics will surely be associated in due course with cognate industries. I t must be stated, however, t h a t there are some branches of science-and these by no means t h e least important ones-which have so little direct relation t o industry t h a t t h e industrial laboratories will certainly neglect t h e m t o some extent, a n d it is for these branches of science, which m a y be termed the “nonpaying” ‘ones, t h a t special provision must be made. T h e whole argument of this article is intended t o show t h a t only a n institution which benefits b y the knowledge which is developed can be expected adequately t o provide for t h e furtherance of t h a t knowledge, a n d if t h e industries do not directly profit by t h e advancement of some branches of science, a n d yet t h e progress of those branches is essential t o t h e welfare of the people as a whole, it is t h e people as a whole t h a t may be justly expected t o provide for their advancement. This is already recognized in the case of some branches of science which have a more obvious a n d direct bearing on the general life of the community. Agriculture, forestry-even zoology in some of its phases, such as entomology a n d piscicultureare already provided for by state or federal institutions, b u t new institutions are urgently required for theoretical physics, theoretical chemistry, mathematics a n d some other branches of physical science. Astronomy is provided for b y private benefaction, provision for the means of obtaining knowledge about the universe at large having apparently been regarded b y a number of wealthy men as a deserving object of charity. It would seem, therefore, t h a t the energies of those who are interested in t h e furtherance of scientific research should be directed toward obtaining adequately staffed a n d equipped institutions for t h e prosecution of those sciences which have little direct relation t o industry, leaving t h e furtherance of t h e branches of science directly associated with manufacturing processes t o t h e industrial laboratories, which are now rapidly springing up t o take their share in the advancement of knowledge. C. E. K E K K E T HM E E S EASTMAN KODAKC O M P A N Y ROCHESTER, N. Y.
ORIGINAL PAPERS OZONE IN VENTILATION’ By J. C. OLSEN A N D WM. H.ULRICH
I n spite of t h e fact t h a t a great many investigations have been carried out in recent years on t h e effect of ozone on air bacteria a n d odors a n d also on the physiological effects of ozone, t h e most diverse conclusions have been reached a n d opinions expressed with reference t o t h e questions investigated. This confusion is due somewhat t o faulty scientific technique a n d 1 Read a t the 6th Semi-annual Meeting of the American Institute of Chemical Engineers, Troy, Kew York, June 17-20, 1914.
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I
deductions from improperly chosen experiments as well as e x $&e point of view. The most recent criticisms against ozone in ventilation are found in two articles which were published in the issue of Segtember 2 7 , 1913, of t h e Journal OJ’ the American Medical Association, one b y J o r d a n a n d Carlson and t h e other b y Sawyer, Beckwith a n d Skolfield on the bactericidal, physiologic a n d deodorizing action of ozone. A number of errors in t h e methods used in the experiments given in these articles have been noted a n d these seem so serious a n d t h e articles have been so
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widely quoted t h a t it seems desirable t o correct t h e misapprehensions which have been produced. Both of these articles refer t o t h e fact t h a t exaggerated claims were made b y agents selling ozone machines. I n t h e article by Jordan a n d Carlson, i t is stated, on page 16, t h a t the concentration of ozone is determined by drawing t h e ozonized air through a solution of potassium iodide which has been acidified with sulfuric acid. T h e liberated iodine is t h e n titrated with thiosulfate solution. It is well known among chemists t h a t a n acidified solution of potassium iodide is readily oxidized by the ordinary oxygen of the air, and, therefore, if a n acidified solution of potassium iodide is used for t h e determination of ozone, t h e results will be high. The amount of t h e error will vary with t h e concentration of t h e ozone a n d may easily give results double the true concentration of ozone. This error can easily be demonstrated b y drawing air free from ozone through such a n acidified solution of potassium iodide. It is evident, therefore, t h a t no reliance can be placed on t h e figures given for the concentrations of ozone which are reported in this article. I n the article by Sawyer, Beckwith a n d Skolfield, the concentrations of ozone were not determined. It is universally recognized by ventilating engineers who are familiar with t h e use of ozone t h a t i t is of t h e greatest importance t o regulate t h e concentration of t h e ozone a n d t h a t ozone is useful only when employed in t h e proper concentration. This well known principle seems t o have been so little understood by these investigators t h a t they failed t o make careful a n d accurate determinations of the concentrations of ozone used a n d therefore many of the conclusions which they reached are entirely vitiated. Another very serious error in experimental procedure is found in the tests which were made on the effect of ozone on odorous substances. A considerable number of such substances were experimented with and t h e conclusion was reached t h a t the ozone m a s k s these odors b u t does not destroy them a n d t h a t , therefore, ozone is not useful in the removal of such odors. T h e method of procedure consisted in exposing the substance giving o f f t h e odor until a marked odor was noticed in the small closed room which was used for t h e experiments. T h e ozone machine was then operated until a strong odor of ozone was produced. Observations were made from time t o time of the odor in t h e room a n d i t was observed in a good many cases t h a t the ozone odor gradually disappeared a n d the odor of t h e substance experimented upon returned. I n some cases ozone was again generated until its odor was pronounced a n d observations again made with reference t o t h e disappearance of the ozone odor and the reappearance of the odor of t h e substance experimented upon. The conclusion was drawn that t h e ozone did not destroy t h e substance giving bhe odor but masked i t ; this conclusion was based upon the disappearance of the ozone odor a n d the return of the other odor. N o other evidence, whatever, on this point is presented. I n these experiments, no a t t e m p t seems t o have been made t o determine the amounts of the odorous
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substances which were present in t h e air except by the odor. T h e experimenters apparently did not consider the fact t h a t t h e odors of substances differ a great deal in intensity a n d t h a t t h e quantities of substances which would be present, even though t h e intensity of the odor was the same, would differ very much. These authors also failed t o keep in mind t h a t t h e destruction of odors by ozone is a n oxidizing process a n d t h a t this, as well as all chemical reactions, is quantitative in t h e sense t h a t a definite amount of oxygen is required t o oxidize a definite amount of a n oxidizable substance. The following reaction takes place when ozone oxidizes hydrogen sulfide:
H&
+ 03 = HzO + S +
0 2
T h a t is, 34 parts of hydrogen sulfide would require 48 parts of ozone for their oxidation. When the hydrogen sulfide is dissolved in water, the sulfur liberated is still further oxidized b y the ozone t o sulfuric acid which would require a still larger quantity of ozone, but according t o the reaction given, a somewhat larger amount of ozone t h a n hydrogen sulfide would be necessary for t h e destruction of this substance. Now, if t h e intensity of t h e ozone odor is much greater t h a n t h a t of the odor of hydrogen sulfide, t h e hydrogen sulfide would be oxidized by t h e ozone in the experiments reported by Jordan a n d Carlson a n d some other authors quoted, and the hydrogen sulfide odor would then return as reported b y these investigators. I n order t o verify these conclusions, experiments were carried out to ascertain the amount of hydrogen sulfide which will give a distinct odor. A large balloon flask of 30 liters capacity was used. T h e hydrogen sulfide myas produced b y treating known weights of carefully analyzed iron sulfide with dilute sulfuric acid. The reacting substances were placed on a watch crystal suspended in the center of the balloon flask. I n addition t o the odor, tests were made with lead acetate paper. I N T E N S I T Y OF O D O R O F
M C . H?S P E R
CUBICMETER 977 244 61 30 15 7.6
HYDROGEN SULFIDE
TESTWITH LEAD
ACETATEPAPER Very black Very black Very black Turned black slowly Brown on edges Turned brown very slowly
ODOR Very strong Strong Distinct Fairly distinct Faint No odor
While t o obtain a distinct odor of hydrogen sulfide. 61 parts are required, t h e odor of ozone is very marked
when present t o t h e extent of one part per million, t h e limit being one-tenth part per million. I n the experiments of Jordan a n d Carlson, the concentration of the hydrogen sulfide must have been from 30 t o 6 0 mg. One part of ozone would have given a strong odor which could mask the odor of t h e hydrogen sulfide until, by t h e oxidation of t h e latter, t h e ozone was decomposed. Less t h a n one part per million of the hydrogen sulfide would be destroyed b y this oxidation, leaving a sufficient amount of hydrogen sulfide t o give a very distinct odor. On again generating ozone until a strong ozone odor was obtained, the hydrogen sulfide would be again “masked,” and when the ozone odor had disappeared the hydrogen sulfide odor would reappear. This could be done repeatedly
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as reported b y Jordan a n d Carlson. The conclusion which they drew, however. is entirely unjustified, namely, t h a t their experiments showed t h a t t h e hydrogen sulfide odor was merely masked a n d hydrogen sulfide not oxidized or destroyed b y t h e ozone. I n order t o verify this conclusion, t h e following experiment was carried o u t : A concentration of z j mg. of hydrogen sulfide was treated with ozone of a concentration of 3 j . 6 mg. per liter. I n these concentrations there would be just enough ozone t o oxidize t h e hydrogen sulfide. I n this experiment the ozone odor was a t first very pronounced b u t after this odor had disappeared there was no hydrogen sulfide odor. A slight acidity was indicated b y t h e reddening of blue litmus paper. T h e ozone used had been very carefully tested for nitrous oxides b u t none were found. Another experiment was carried out in which t h e ozone concentration was 7.6 parts per million, while t h e hydrogen sulfide concentration was 60.7 mg. per cubic meter so t h a t only a small part of t h e hydrogen sulfide could be oxidized b y t h e ozone present. At first only t h e odor of t h e ozone could be detected. The hydrogen sulfide odor gradually returned so t h a t within one hour a faint a n d after two hours a distinct hydrogen sulfide odor was detected while t h e ozone odor had entirely disappeared. This experiment could be repeated three or four times, as reported b y Jordan and Carlson on page 3 3 of their article. They further s t a t e : “The mechanism of this masking action of ozone does not concern us here.” If t h e authors had considered t h e “mechanism” of this action, they might have reached entirely different conclusions a n d would have seen t h a t their experiments were in exact accordance with t h e theory t h a t ozone oxidizes hydrogen sulfide a n d other substances. They still further refer t o the fatigue of t h e olfactory end-organs b y t h e ozone. They say “Strong concentrations of ozone rapidly fatigue or anesthetize the olfactory epithelium.” One wonders why t h e authors did not make this statement general and state what every chemist has frequently observed t h a t h y d r o g e n sulfide a n d the numerous other odors which are present in chemical laboratories produce t h e same effect on olfactory epithelium so t h a t these odors are not noticed b y workers in t h e laboratory. Hydrogen sulfide is also oxidized b y t h e air as is shown b y t h e fact t h a t t h e odor slowly disappeared in a duplicate experiment in t h e absence of ozone. I n some cases ozone acts as a catalytic agent. This was shown by t h e action of ozone on linseed oil Weighed quantities of linseed oil were exposed t o air a n d ozone. The oil exposed t o air gained 1 7 mg. while a n equal quantity exposed t o t h e action of ozone gained I I O mg. during t h e same time. The amount of ozone generated was 11.4 mg. T h e ozone, therefore, acted as a catalytic agent, causing t h e absorption of 8 2 mg. of oxygen which is nearly five times as much oxygen as was absorbed b y t h e oil exposed t o air alone. It is reasonable t o suppose t h a t ozone would act a s a catalytic agent a n d cause t h e oxidation of other oils a n d organic substances similar t o linseed oil. I n t h e case of ammonia, t h e same considerations
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apply. Ammonia is oxidized by ozone in accordance n-ith t h e following equation: zSH3 3 0 3 = Nz 3H20 302 I n this case, one part of ammonia is oxidized b y about four parts of ozone. X study of t h e intensity of t h e odor of ammonia gave t h e following results:
+
+
+
IXTENSITYO F T H E O D O R OF .%MMORIA MG. NH3 P E R CUBICMETER TESTWITH L I T M ~PAPER S ODOR 1000 Turns blue readily Turns blue slowly 659 Turns blue slowly 329 165 Turns blue very slowly Fairly strong Quite distinct 82 Turns blue very slowly 41 Turns blue on edges very slowly Faint 21 Turns partially blueon edges very slowly Very faint 10 No action No odor
Experiments were carried out in which known amounts of ammonia were treated with definite amounts of ozone a n d t h e ammonia remaining was determined b y absorption with sulfuric acid and nesslerizing. Ammonia is acted upon very slowly so t h a t 2 4 hours were allowed for t h e reaction. The concentration of t h e ozone was 3 5 . 6 mg. a n d of t h e ammonia, 125 mg. per cubic metcr. After 2 4 hours, 78 mg. of ammonia remained in t h e flask containing air a n d i j mg. in t h e flask containing ozone. The quantity of ozone prcsent was sufficient t o oxidize S1;’? mg. of ammonia per cubic meter. The experiment indicates some oxidation of ammonia b y ozone. Erlandsen a n d Schwartzl state t h a t their results showed no action of ozone on ammonia. Experiments were also carried out t o ascertain t h e intensity of t h e odor of oil of cloves. It 1%-asfound t h a t 6 6 mg. per cubic meter would give a strong odor. T h e amount of ozone necessary t o oxidize oil of clovcs cannot be calculated exactly b u t i t would probably require several times inore t h a n an equal weight. On subjecting t h e oil of cloves vapor i n a concentration of 36.6 mg. per cubic meter t o t h e action of ozone of a concentration of 33 mg. per cubic meter, i t r a s found t h a t a t first a distinct odor of ozone could be detected which gradually disappeared a n d was replaced b y a sweet odor which had no resemblance t o t h e strong odor of t h e oil of cloves. Very evidently t h e oil of cloves or one of its strong smelling constituents is oxidized, at least partially, so as t o leave a n organic compound having an entirely different odor. T h e flask was allowed t o stand a total of 2 1 hours although t h e reaction was practically complete within z t o 3 hours. The reaction did not seem t o be entirely regular. The experiment was repeated several times and t h e formation of t h e sweet aromatic substance repeatedly observed b u t a t times t h e odor of cloves persisted. Any excess of ozone was removed b y shaking with I O per cent ferrous sulfate solution. Control experiments were also made with a balloon flask containing oil of cloves a n d air only. Erlandsen a n d Schwartz have made a similar observation with respect t o skatol a n d indol. They state t h a t these substances are completely decomposed b y ozone with t h e formation of pleasant smelling substances similar t o coumarin. They also state t h a t mercaptan is rapidly decomposed b y a large excess of ozone. These authors also found t h a t hydrogen sulfide is oxidized b y ozone. Jordan 1
Zeit. of H y g . , 1913, pp. 81-100.
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a n d Carlson also mention t h e work of Erlandsen a n d Schwartz b u t state t h a t t h e results of t h e latter agree with those of Jordan a n d Carlson in showing t h a t ozone m a s k s odors a n d does not oxidize the substances discussed. Jordan a n d Carlson even state t h a t “ T h e inability of ozone t o oxidize (to a n y appreciable ext e n t ) ammonia vapor a n d oil of cloves is very striking.” Franklin gives t h e results of experiments showing t h e oxidation of a great many organic substances a n d demonstrated t h a t carbon monoxide is oxidized t o carbon dioxide? Undoubtedly m a n y of t h e conflicting conclusions which have been reached are due t o t h e failure of experimenters t o t a k e into account t h e quantitative relations between ozone a n d t h e substances t o be oxidized a n d have generally failed t o realize t h a t on account of t h e much greater intensity of t h e odor of ozone t h a n t h a t of other substances producing odor far too little ozone has been employed i n t h e experiments. T h e odor of ozone is a t least I O O times as intense as t h a t of other substances having a pronounced odor. T h e common method of using ozone t o destroy odors seems t o be justified b y these considerations. T h e ozone machines in good practice are operated so t h a t a very small concentration of ozone in the air is produced. T h e continued renewal of this small a m o u n t of ozone oxidizes t h e odorous substances a n d gives t h e total quantity of ozone required by chemical theory. Jordan a n d Carlson undertook t o prove t h a t ozone does not destroy smoke by coating a piece of glazed paper uniformly with a thin film of lampblack a n d subjecting t h e carbon t o t h e action of ozone for I O hours a n d state t h a t there was no effect on t h e lampblack. T h e y regard this as evidence t h a t ozone does not destroy smoke although t h e y state t h a t smoke also contains carbon monoxide, sulfurous acid, etc. T h e y seem to have made no a t t e m p t t o study t h e effect of ozone on carbon monoxide a n d sulfurous acid b u t state t h a t t h e assertion t h a t “ozone destroys smoke” is equivalent t o a deliberate deception because ozone does not oxidize carbon particles suspended in the air. Not being chemists, Jordan a n d Carlson might not have known t h a t carbon is extremely difficult t o oxidize b u t t h e y should have known t h a t carbon monoxide a n d sulfurous acid as well as creosote a n d other pungent a n d aromatic organic substances present in smoke produce disagreeable a n d toxic physiological effects. It is just these constituents of smoke which are easily oxidized b y ozone. T h e carbon which is not acted upon is totally inert a n d harmless. J o r d a n a n d Carlson also carried out investigations on t h e action of ozone o n air bacteria. As has already been stated, their determinations of t h e concentration of ozone cannot be relied upon because acidified solutions of potassium iodide were used which give high results. T h e authors admit t h a t t h e plate method which they used was not a n exact one a n d t h a t therefore t h e results were irregular. T h e y obtained a reduction of bacteria from 64 t o 38, 49 t o 18, 61 t o 67 (increase), 78 t o 34; t h a t is, t h e bacteria were reduced t o 40.6 per cent, 63.3 per cent a n d j6.4 per cent in 1
Heating and Venlilnling Magazine. 10, No. 11.
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three tests, while in t h e fourth there was a n increase t o 109.8 per cent. Most authors would discard t h e fourth test a n d consider t h e reduction t o be a b o u t 55 per cent. Jordan a n d Carlson then tried Winslow’s more exact method but did not use a large enough sample for t h e test (4.5 liters) so t h a t t h e highest number of bacteria counted was 7. It is not good practice in bacteriological work t o rely on counts of so small a number. Jordan a n d Carlson draw t h e following strange conclusion from their iesults: IL 2-The aileged effect of ozone o n t h e ordinary air bacteria, if it occurs a t all, is slight Hnd irregular even when amounts of ozone far beyond the limit of human physiological tolerance are employed.” There is no reason t o suppose t h a t t h e ozone used in these experiments was “ F a r beyond t h e limit of h u m a n physiological tolerance.” T h e reduction in t h e number of air bacteria is not “slight a n d irregular.” T h e experimental results of Jordan a n d Carlson agree with t h e results obtained by one of us1 in New York school rooms showing a reduction in air bacteria a n d moulds of 7 5 per cent, 91 per cent a n d 91 per cent, t h e greater reduction resulting from longer exposure t o ozone. K O ill effects were observed on t h e children a n d adults present during these tests. Jordan a n d Carlson (p. 34) state: “Some bacteria are undoubtedly killed b y ozone, especially if t h e y are in a moist condition.” This statement is correct as it is generally recognized t h a t ozone destroys moist bacteria very rapidly. T h e conclusion drawn b y Jordan a n d Carlson is very far from being correct. They s a y : “ I n practice, however, t h e fact is of very slight importance.” T h e works of Chapin, D o t y a n d of Winslow a n d Robinson have fairly disproven t h e belief held so long t h a t bacteria existed as a menace in rebreathed air. It has been shown t h a t infection occurs b u t rarely from air-born bacteria a n d then only when the bacteria are in the moist c o n d i t i o n . It is just these virulent bacteria which are quickly destroyed by ozone even in low concentrations. T h e bacteria which resist t h e ozone are powerless t o transmit disease. It is by no means necessary t o show t h a t ozone is capable of sterilizing t h e air in order t o show t h a t i t is useful in ventilation. There is in fact no other disinfectant which can be used even in low concentrations in living rooms. All other known disinfectants are highly dangerous in concentrations high enough t o be a t all effective. Ozone in low concentrations will both remove odors a n d will materially reduce t h e bacteria content of the air. Jordan a n d Carlson a t t e m p t e d t o show t h a t ozone is dangerous by subjecting guinea pigs t o high concentrations until t h e animals died. They also forced strong ozone ( I O parts per million) directly into t h e lungs of dogs a n d rabbits after performing tracheotomy under ether a n d inserting a tube well below t h e larynx a n d treating t h e wound with cocaine. They say they did this because a t least three-fourths of t h e ozone is decomposed b y the mucous membrane of t h e respiratory 1 “Purification of Air and Water by Means of Ozone,” Olsen, Fourth International Congress of School Hygiene.
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1914
T H E J O li R N A L 0 F I N D U S T RI A L A ATD E N GI
passages. It is difficult t o see what bearing this experiment can have on t h e use of ozone in ventilation. T h e ozone which was forced into t h e lungs must have been several hundred times as concentrated as i t is ever used i n ventilation. It would have been quite as logical t o place animals in pure oxygen or even in a n atmosphere of jo per cent oxygen a n d also force these gases directly into t h e lungs. When t h e animals died a n d t h e lungs were found. t o be inflamed, t h e conclusion might be drawn b y highly academic experimenters t h a t i t is dangerous t o breathe air containing 2 0 per cent oxygen. Jordan a n d Carlson carried out experiments with what might be called low concentrations of ozone. T h e y subjected 4 cats, 4 rabbits, 6 guinea pigs a n d 1 2 rats t o ozone of I part per million nine hours daily during two weeks s o t h a t irritation of t h e eyes a n d nose was produced. Body weight, appetite a n d general condition were noted. N o ill effects on appetite a n d body weight or general condition could be observed. The conclusion could, therefore, be drawn t h a t ozone in moderate concentrations is harmless b u t Jordan a n d Carlson warn us t h a t this conclusion is not justified. They say: “We desire t o state, however, t h a t this test does not warrant t h e conclusion t h a t the ozone in concentrations t h a t m a y be used in practical ventilation is harmless t o man. T w o weeks is a short time in t h e life of a man. If ozone i n ventilation should come into general use, i t would mean in t h e case of office a n d shop workers exposure t o ozone from six t o t e n hours a d a y , six days of t h e week, from nine t o twelve months of the year for from t w e n t y t o fifty years. And even if this prolonged exposure t o ozone should prove harmless t o t h e robust person, what about t h e unfortunate person whose lungs have only slight power of resistance?” Jordan a n d Carlson seem t o have fallen into t h e error of assuming t h a t because they have not tried t o , a n d therefore have not demonstrated actually, benefit from t h e use of ozone, this is equivalent t o having demonstrated t h e reverse, i. e . , t h e harmfulness of ozone If t h e facts presented in this paper are properly interpreted they will be found t o be i n accordance with t h e view t h a t ozone is a powerful disinfectant a n d deodorizing substance, which, i n suitable concentration, is without a n y injurious effects whatever. T h e elimination of odor is b y no means t h e least important function of ozone a n d there is no other agency available except dilution with fresh air. I n m a n y cases it is impossible t o introduce enough air for t h i s purpose without producing annoying a n d dangerous drafts of air not t o mention expense of blower installation a n d operation as well as heating t h e air. As a matter of fact, before ozone was available, disagreeable odors have often been considered unavoidable nuisances which could not be eliminated or overcome. With reference t o t h e alleged harmful effects of ozone, n o single instance of h a r m t o a person from t h e proper use of ozone i n ventilation has been published b u t all adverse opinions have been deduced, b y inference, as i n t h e paper b y Jordan a n d Carlson, from
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experiments performed with very high concentrations while all efforts t o produce harm experimentally with weak ozone have failed. Jordan and Carlson report t h a t twenty-six animals, exposed for fourteen days, during nine hours each day, t o concentrations high enough t o cause irritation of t h e eyes a n d nose, suffered no ill effect whatever. Hill cites t h e cases of t h e numerous workers in t h e London underground tubes who have shown no ill effect in three years. Gminder cites t h e unharmed workers in t h e spinning mills a t Reutlingen. and numerous similar instances of prolonged proper use of ozone without a single complaint are today in existence. T h e Jordan a n d Carlson report is t h e most elaborate a n d convincing laboratory test t h a t has been published. POLYTECHNIC INSTITUTE, BROOKLYN
THE FLUORESCENCE OF PETROLEUM DISTILLATES B y BENJAMIN
T. BROOKSA N D RAYMOND F. BACON
Fluorescence is one of t h e most striking characteristics of petroleum distillates b u t its cause is not known, at least some of our best authorities attribute i t t o causes which have nothing t o do with t h e phenomenon. T h e heavier distillates from Pennsylvania a n d certain other crude petroleums have a marked greenish fluorescence, a n d t h e trade has come t o associate this property with Pennsylvania oils. For some i s e s i t is common practice t o “debloom” the oils by sun-bleaching or b y t h e addition of certain “deblooming” substances. T h e subject therefore has some practical as well as theoretical interest.2 Engler considers t h a t t h e fluorescence of mineral oils is due t o their colloidal character. Crude oils a n d t h e heavier distillates are optically nonhomogeneous and show a marked Tyndall effect, b u t thisproperty cannot be considered as indicating colloidal properties since many organic compounds having large molecular weights show t h e Tyndall effect when i n t r u e solution. Schneider a n d Just3 claim t o have observed ultramicroscopic particles in a “yellow mineral oil” a n d a sample of “paraffin oil.” Holde14 studying t h e physical condition of lime soaps in grease, stated t h a t colloidal particles are not discernible a s such under t h e microscope. I t is probable, however, from t h e researches of Holde t h a t such greases, as well a s oils containing asphaltic or resinous matter, are t o be regarded as colloidal, not true solutions. Schulz5 claimed t h a t the effect of adding “deblooming” substances, such as nitrobenzol a n d nitronaphthol, was merely t h a t of adding something having a high refractive index, t h u s making t h e oil optically homogeneous. This theory of t h e fluorescence of mineral oils seemed very plausible. However, since m a n y examples of nonfluorescent oleo-resinous solutions a n d mixtures 1 Presented at the 49th Meeting of the American Chemical Society, Cincinnati, April 6-10, 1914. 9 Cf. “Relations between physical Properties and Constitution,” Kayser, “ Handbuch d. Spectroscopie,” Vol. IV, p. 839; Kauffmann. ‘‘ Beziehungen zw. Fluoreszenz u. Chem. Konstitution,” Snmml. Chem. U. Chem.-techn. F’orfrllge, 11, 1906. a 2. f. wisiensch. Mikroscopie, 1906, p . 489. 4 Z . f. angew. Chem., 31 (1908). 2138; Koll. Zfschr., 3 (1908), 270. 5 Petrol. Bert., 6 , 2 0 5 .
