Rise of Air Conditioning' With Particular Reference to the Chemical Field W. L. Pleisher i t WE>, 4LN" 5*
1,'IXOUGH one call iinnlly say tliat a imtn or a law establishcd a ~ l m n c h of scioi discoveries of Ihyle in t,lie mil oi Dalton, Gayl,iiisac, and t'lia later, certainly est,atilisiied t,Iv gas Itiws on wliicli ttieuret,ically air conditioning is iiased. Xoyle's law, wliirli states t,hat at a constant temperatiire tlic volunio of a given quarrtity of nny gas varies inversely as tlic presmre to whieli i i is suljevted, oft,en expressed ns pi' = a const,:int, and Ualton's law, wiricb says that the prwsure esert.eiS by a mixture of gases is eqind to the sum of th: separate pri!ssures which each gas w d d exert if it occilpied the whole volume, ofterr expressed as 71V' = ), are t h twj basic laws of air cmdit,ioiiing. It is also inkreit,irig to remember that both Boyle and Dalton w-ere primarily cliemists and that many of the imic chemical discoveries were made by then! (Boyle wns the discoverer of piiosphorus and I>alton enunciated the theory of color blindness). One can therefore readily see tliat eliemixtry and ajr eoiiditioning were of similar growth, that one arm? from the practice of the other, and that air coriditioiiing as emhracad in the fundamental laws of physics is a conception of chemistry, Of conrse today, with our new kiaiwledge of chemistry, we might have to state that both chemistry atid air conditioning, as welS as all of physics, are o d y a part of the general science of electrophysics. Ifowever, as we proceed in the development of the different mts and sciences, chemistry and air conditiuning, and one might say also physics, tend to separate widely, and it is only in tho 1 s t few years that a more scientific iiiveiitigation of air conditioning has brought them together aKain. In fact, only within the last few months was the first suggestion made of an analytical method of detemiining the proper air eonditioris ' ir was based on the cliernistry of the object with u4iich the a' brought into contact. It i s customary to define air conditioning as the simultaneous cont.rol of temperature, m o i s t u r e content, and air movement. In away this d e f i n i t i o n goes too far. and in a way it falls short of being complete. However, it is true that aSS three of these factors affect the surrounding objects. I t s incompleteness consists in the neglect of their relative values. The early scientists were interested solely in the theoretical or t h e philosophical conception of their
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Received April 17, Fisure I -Complete Dehumidifyinn
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irivcstigiitioiis :mi their discoveries. I t was not until moilern intiustry r:rcated a riecexsity for onifonnity or qitant,ity produethm that air ~ontlitiorrirrg hecame a hrancli of science OS importance to everyone. Air conditiouing actually was used in iiiakiiig of lenveired l m x l alrnost frorr, the begiiming of tton or pictorial Iiist.ory. But there is a question as to whether, in the light of our present knowledge of colloidal cliernistry, t i i s so-called air conditioning in the baking indur t,ry or in the l ~ ~ i n d i obaking ld process was a true air-conditioning pr011Sem. r . 1 hat moisture evaporated fnrm danirnpened clotiis was definitely nseci during the frrnir:ntation process is well es(if years pa~sedt d u m a true t,ablislied, but many Siundr :i,ir-coiidit,ioning iiistallation on any scale was attempted, and t,liis first appear4 in tlie textile industry, It was d i s covered i i i tlic eiglrteent,lr century, when textili,s were first marlc in Srirga qumt~itiesin centralized factories, that either tiin hctnries rrmit Iic establislied in climates whicb were miiform in t~mpcratore,wnnlly cool and with a liigli pcrcentagc of moistnre, or that. t i m e conditions, even in a crudc way, by mechanical moans. f rently to diffcrent condit tnre, moistiire, and nir mi~vemcnt. l'ractioally all celliilar sirbstancen lost or gained weight according t o the condition of the surronnding at,mospliere. In dry climates or on part,iculrrrly dry days, which usiially occurrod when the tcmperat,nre was liigli, static c1cctricit.y made it difficult to operate machines or to produce iniiform g o d s . :I'liese conditions ncre first relieved by the intmductiim of steam into the atumsplrere. Steam corresponds almost esactly to tlie gaseous muistore wiiiati is an inherent part of the atmosphere. When released into the atmospliere it is atisorhed to a certain extent by the air, and the moist,ure in the air when brought in eontact with celiuIar m a t e r i a l is absorbed by the material, whicli gains in weight, and usually in pliability or uniSormity, and exhibits less static electricity than before the nioisture wa8 a d d e d . Today we are iiiclined to b e lieve that this m a t e rial is colloidal in nature and condenses the gases brought in contact with it and holds the added moist.nre t e n a c i o u s l y a g a i n s t its sides or cells. Whatever we may call the moisture that is added, there is no doubt that it attaches itaelf tenaciously to SYBtem with Separate Coolin* Tank
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INDUSTRIAL A Y D ENGI.VEERI,VG C H E * I S T R Y
dry-bulb temperature are those corresponding to any heating or cooling problem. Industries Dependent on Air Conditioning Man's reaction to the atmosphere around him is historical. It requires no elucidation. It is one of h'ature's primary thoughts. In himself man, when properly nourished, has the ability to manufacture alleviating or compensating conditions to offset the inequalities of weather. The human body is the finest conceivable air-conditioning machine and with all our progress in the art, our automatic control or balancing of temperature and moisture t o meet changing conditions does not approach the work done by the various apparatus that is part of our bodies. Biology and medicine are being put to work to acquire sufficient knowledge to rebuild, refire, or refuel human beings, so that the machines they own will act efficiently, but without chemistry the biologist, the physicist, and the physician are lost. Today the major development of air conditioning is in the comfort field. Much might be written on what is being done in the hospitals, picture houses, banks, and homes to make people comfortable. But air conditioning got its start in industry and a great deal that we learned about it originated from that source. The writer's start in air conditioning was in the candy and bakery fields. Both mere controlled by chemists or by rules laid down by chemists and translated into rule-of-thumb methods for the production of proper goods. In candy, particularly chocolate, temperature and humidity affect the color and consistency of the surface, the drying of the starch in which the filler is set, and the storage of the finished goods. I n hard candies the adsorption of surface moisture and excess moisture or heat change the nature of the sugars and affect the bottling or packing of the candy. These are all chemical problems. In the bakery, ferrnentation, colloidal behavior, surface phenomenon-also chemical problems-are the reasons for the need of definite and uniform air conditions and the chemist was instrumental in discovering them and suggesting a solution. That the electrophysicist may enlighten the chemist by further analysis is in no way derogatory to the work the chemist has done. The modern methods of making matches, surely a chemical problem as far as the ingredients go, are absolutely dependent on air conditioning; and the handling of inks and rolls in printing required the combined efforts of the chemist and air-conditioning engineer to secure the proper control of the surrounding atmosphere. Photography and the drying of siccative coatings involving a linseed oil base are also airconditioning problems. The latter required the chemist to discern the catalytic effect of the moisture of the air on the oxidation of the surface before a solution was reached. The pulp and paper industry, a colloidal development in which the immense amount of moisture to be removed was held SO tenaciously, is another example. One industry after another yielded to the combined efforts of the chemists and the airconditioning engineer. Then, about thirty years ago, the manufacture of artificial silk came out of the chemical laboratory. Here a synthetic material produced by the chemist was unmakable without the air-conditioning engineer, and the two groups joined hands to further a great industry. Artificial Silk and Air Conditioning All the varieties of artificial silk, or rayon, which are employed today are pure cellulose to which the luster of natural silk has been added by chemical means. They differ from the silk of the silkworm in that they contain no nitrogen. Chemists have developed five methods of making artificial silk as follows: (1) Chardonnet, made from nitro-cellulose; (2) cuprammonium rayon, made from a solution of cellulose in ammoniacal copper oxide; (3) viscose, made from thio-
Vol. 23, No. 7
carbonate of cellulose; (4) a type of silk made from a solution of cellulose in zinc chloride; ( 5 ) acetate silk made from acetic anhydride. We will not go into the chemistry of these various processes. It is interesting, however, to note that the following things were found essential to the manufacture of the Chardonnet silk: (1) perfect drying of the cellulose a t a definite temperature, an air-conditioning problem; and (2) washing of the partially dry products to be conducted without rise of temperature. Whatever the nature of the manufacturing process may be, the cellulose in its various stages up to the spinning must be handled in a definite temperature, usually around 68" F., requiring refrigeration as well as air movement to maintain these conditions. From the chemical and aging stage it is taken through a spinning process. The spinning room presents an air-conditioning problem of considerable complication because the cellulose, after further chemical treatment and wire drawing, is wound on spools or twisted a t high speed and a definite percentage of moisture in the air is necessary to uniform spinning. Moreover, the chemicals used in the process are usually so injurious, particularly to the eyes of the workmen, that large quantities of air must be passed over the attendants to preserve their health. This large quantity of air is then usually exhausted through the spinning frames or machines and, if it were not of the proper temperature and humidity, it would injure the material being spun. In the spinning room conditions above 85" F. and under 70 per cent relative humidity react unfavorably on the wet fiber and higher temperatures and humidities make it very uncomfortable for the workers. The preliminary drying and the final drying of the finished filaments are done a t a definite temperature starting with a high temperature and coming down to practically room temperature before the bobbins holding the silk are removed. Although this might be construed as a drying problem, all drying problems in connection with artificial silk are actually air-conditioning problems. After the spinning, which as previously stated is very often combined with twisting, artificial silk goes through the reeling process which also may combine a secondary twisting. Here air conditioning is essential to the quality of the finished material. Like all fibrous material, artificial silk has a definite moisture regain, and this can only be obtained with the proper temperature and humidity. A dry-bulb temperature of 74" F. and 70 per cent relative humidity will give approximately 11 per cent regain, which is the best condition for artificial silk. Furthermore, this condition of the air, in some as yet undiscovered s a y very closely associated with the isoelectric state of the colloidal cellulose, allows a freer working of the material, less breakage, and less static electricity. As a large amount of power, and consequently heat, is required for the twisting and reeling of silk, the air conditioning must be supplemented by refrigeration to maintain ideal conditions, In those cases where the finished silk is not run on bobbins but is kept in the skein, the silk goes from the reeling room to an inspection room and each skein is carefully inspected for quality. I n inspecting silk, the hands are passed over the finished silk for the purpose of detecting flaws and a t the same time judging the quality and color. With temperatures above 72" F. and relative humidities over 60 per cent the perspiration from the hand is transmitted to the finished skein and leaves marks on the silk. This does not occur when inspection rooms are maintained a t 70" or 72" F. and 60 per cent relative humidity by means of airconditioning and refrigeration equipment. Conclusion The rise of air conditioning and the influence of the chemist on this particular branch of science have been described. The basic laws of thermodynamics which underlie all problems
July, 1931
IND UXTRIAL AND EXGINEERING CHEMISTRY
in which air conditioning is involved were developed by pioneer chemists. In one industry a t least, the rayon industry, air conditioning is absolutely necessary for continuous production. As it is the writer’s opinion that the hydrogen-ion concentration of all colloidal materials, a function of the electrical equilibrium of the material, can be balanced against the
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hydrogen-ion concentration or the electrical equilibrium of the surrounding air, he believes that the future field for research is one for the chemist, the air-conditioning engineer, and the physicist or the electrophysicist, working in conjunction with each other, t o develop a complete analytical method of determining proper conditions for industries as well as general comfort.
Recent Developments in Corrosion Prevention of Ferrous Metals’ V. V. Kendall and F. N. Speller NATIONAL TUBECOMPANY, PITTSBURGH, PA.
HIS is a review of the principal outstanding developments in corrosion work during the past year or two. Although considerable progress has been made in combating this waste of material, it is well known that much remains to be done, so both the accomplishments and the work that it seems should be undertaken next have been included. This paper is not intended to be complete, but covers the more important activities, particularly in the oil industry. As corrosion prevention is an economic problem, its solution must be based on the cost of preventive measures compared with the loss directly and indirectly due to deterioration. This problem is recognized as of primary concern to purchasers of metal construction, but well-established manufacturers are also interested and glad to cooperate in working out an economical solution. Some effective cohperative work is being done to this end both here and abroad. In fact, this is a world-wide problem that apparently can be solved most readily by non-competitive cooperative research, Recent work on the fundamental processes of corrosion has been done mainly on the study of metal surface films and potentials. Evans (3) has done some interesting work in connecting changes of potential with film formation and has utilized these potential changes in tracing the formation of films. His previous accomplishments in the separation of these invisible films from the surface of metals are well known (11). Passivity has been satisfactorily connected with the formation of primary stable oxide films. The presence of these films has been indicated or proved by (12):
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attack, a middle value slight rusting, and a low value profuse rusting. Figure 1 has been slightly changed from the original to give the analysis and surface condition of the metals. The metals were either ground coarse or polished by successively finer grades of emery, cleaned with carbon tetrachloride, and exposed to air, free of dust and moisture, for 1 week. This would result in the formation of a film of some description before the initial measurements were taken. The increaFed resistance of chromium steels to corrosion in the polished condition is well known and is readily shown in the potential curves. Chromium has the power of forming a very resistant (invisible) film in oxidizing media, but in dilute hydrochloric acid, where such films cannot exist, it dissolves even more rapidly than pure iron. Recent developments have demonstrated that the study of films which has been in progress for the last few years is of the utmost practical as well as theoretical importance. Films can either inhibit or accelerate corrosion, depending upon their physical properties, potentials, and continuity. Discontinuous films are the main cause of pitting. The artificial production of dense, tightly adherent, or continuously produced,
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Improvement in methods of making potential measurements has permitted the determination of the course of the potential curve with time. The results of such measurements, such as the work of Evans (3) in Figure 1, correspond to the behavior of the film,a rising potential indicating that weak points are being repaired and a falling potential that the breakdown is extending. A high h a 1 potential indicates immunity from 1 Received March 21, 1931. Presented before the Western Metal Congress, San Francisco, Calif., February 18 to 20, 1931.
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g (1) The inability of “air-oxidized” iron to plate out copper from a copper sulfate solution. ( 2 ) The resistance to corrosion imparted to iron by immersion in solutions of oxidizing salts, such as chromates. (3) The resistance to the flow of current through iron, nickel, and cobalt electrodes after anodic oxidation. (4) The inactivity of metals having basic oxides in neutral or alkaline media and their subsequent activity in acids in which the solubilities of the oxides are greater. ( 5 ) The actual presence of tough, thin, transparent oxide films on “air-passive” materials as determined by their isolation from carbon and stainless steels by selective dissolution of the underlying metal.
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Figure 1-Potentials
of Commercial Steels (Bannister and Evans)
self-repairing films will solve many corrosion problems. The use of sodium silicate and of dichromate in refrigerating and other solutions are well-known examples of such applications. Bengough, Stuart, and Lee ( 4 ) have developed more refined means of determining initial rates of corrosion by measuring the oxygen consumed in a closed-type apparatus. The electrolytic theory still explains satisfactorily most of the problems in the corrosion of metals, the outstanding
