ustry since the four largest usages are in idustries that are relatively young and rowing. In this usage chart, pyramiding has been jduced as much as possible and corre>onds more nearly to sales tonnage rather lan the production tonnage. T h e circle ^presents about 6 billion pounds. The rubber segment is probably abonnai. In 1945, 900,000 tons of synthetic ibber were made. This went up slightly - t o a million tons in 1946—and plans in 947 are for about 500,000 tons. There is Ptlk that in subsequent years this might jvcl off at 250,000 tons. If it does, this îgment, instead of being 1.4 billion lb., 'ill be nearer 750 million. While this segîent is made up principally of butadiene, 'hich is three fourths of GR-S rubber, it Iso contains substantial quantities of hloroprenc monomer for the manufacture f Neoprene, isobutylene for the manufacurc of butyl rubber, and a much smaller uantity of acrylonitrilc for Buna N. The automotive segment is larger in 946 and will continue to be so in future ears. The products making up this segment arc mainly the glycols and alcohols ised in the antifreeze systems and the thylcne dibromide used in tetrae thy Head. is well as the ethylene dichloride and the ithyl bromide used for dissolving the •etraethyllead. The next use from the standpoint οι size s plastics and resins. This is probably the astest growing outlet for aliphatic chemijals. From the viewpoint of tonnage, ormaldehydc tops the list even if the water .hat the Tariff Commission retains in the 57% formalin is excluded. This is followed closely by acetic anhydride for making icetate plastics. The fastest growing group is the vinyl chemicals, such as vinyl chloride and vinyl acetate. T h e plastics segment also includes the acrylates, mclELminc, urea, polyethylene, and pentaerythritol. Interestingly enough, the 1945 Tariff Commission's estimates show that almost exactly an equal amount of aryl and aliphatic resins were made—both about 400 million lb. There are some plastic enthusiasts who would also adopt the next family—the synthetic fibers. In the case of rayon, each of the three most important types of fibers requires aliphatic chemicals—acetic anhydride and acetone to make cellulose acetate, carbon disulfide to make the xanthate type of fiber, and the polyamides to make nylon. T h e next in size, surface coatings, is also a close kin of the plastics group, in that the film-forming solids are frequently syn thetic resins. However, the quantities .of aliphatic derived resins are not nearly as important in this field as are the aryl de rived resins, due to the great popularity of the alkyd resins derived from phthalic anhydride, which in turn is derived· from coal tar naphthalene or petroleum derived o-xylenc. This 8.4% segment of aliphatic surface coatings is principally made up of
VOLUME
2 5,
NO.
the ester and ketone solvents used to de posit protective coating films. The rest of the chart illustrates the rela tively unimportant part played by the ali phatic chemicals in the older industries. Relatively small quantities are used in metal processing and in foodstuffs. In the case of foods, which include agricultural uses as well as food processing, the seg ment includes such products as the Freon refrigerants and urea for fertilizer. In metal processing, the biggest products are the solvents used for the degrcasing of metals. In explosives the 4 % represents mainly the ethylene glycol used for making the lower freezing dynamite. It also in cludes some ether for the manufacture of smokeless powder. Although the tonnage going into the medicinal field is low, it is probable that the relative dollar value is much greater. Future
Developments
In the past, markets were developed by three principal methods. One was finding a new use for an old product, such as the use of triethylenc glycol for air steriliza tion. Another was the development of a new process making possible lower costs, and hence opening up new fields. A prime example of this occurred in cellulose ace tate rayon. When synthetic acetone was introduced, the price decreased from 14 to 7 cents per pound. The same thing happened to acetic anhydride and as a re sult, cellulose acetate rayon made from these raw materials is now selling at almost the same price as xanthate rayon. Thirdly, progress has been made by developing a product with a combination of properties of specific interest for particular applica
tion. A good example is the new tough ened Carbowax compounds. These three methods will pro-bably still be the important paths of future maxket development. In the future, probably there will be more custom building done, that is, more complicated molecules will be tailor-made for the need at hand. A good example is in the case of the resin plasticizers where it is now possible n o t onLy to get a good all-around plasticizer, sucli as 2-ethylhexyl phthalate, but also special plasticizers with either extremcLy good, lowtemperature characteristics, o r greater resistance to water extraction o r witfci in creased flame resistance. Another field in which a great deal of tailor making of molecules is necessary, and one that has been barely scratched, is the field of biological products. Vlany industrial research laboratories now have special divisions engaged in designing new molecules which will kill a fungus bu"t not injure green plant foliage; rcp»el a fly but not irritate human skin; immobilize air borne bacteria but not harm the human respiratory system, or possess some other useful combination of biological prope-rtics. The rapid growth of the synthetic ali phatic industry should continue and per haps accelerate. Each new coinpound may be regarded as a hand from Λνηίοη more chemical digits will grow. Acknowledg
merit
The authors wish to acknowledge the assistance of C . A. Sctterstrom and P. R. Rector in the compilation of s-tatistios and preparation of this paper. PRESENTED before the New York Section of the AMERICAN CHEMICAL SOCIETY and a n Chicago b e
fore the Technical Service Association of t h e Chemical Industry. Part I appeared in th.e Nov» 3 issue of C&EN.
Helium Isotopes Separated by Fluid-Plow J\. SINGLE-STEP process for the separation of helium 3 and helium 4 has been reported by a group at Ohio State University. The process utilizes the super-fluid flow characteristics of helium II and serves as partial verification for the suggestion that He 3 atoms do not partake in superflow, at least not within the limits of measurement. At temperatures near absolute zero liquid helium acquires the property of super-flow, that is, the ability to climb out of its container. This point is known as the λ-point. It is possible that the λ-point of He 3 is below that of He 4 and that when lower temperatures are reached it may also be capable of super-flow. In the experiments at Ohio State, liquid helium II at 1.5° K. was transported by super-fluid flow through a suprasurface film for a given period of time from one reservoir to another, contained within the first, with a resultant concentra tion of the rare He 3 isotope (normally present in atmospheric helium at about one part per million) in the initial res
45 . N O V E M B E R
10,
1947
ervoir. Work is now being carried ou-t on obtaining strong concentrations o i He 3 through the use of large quantities of liquid helium. Concentration of the He 3 isotope whichi is expected to differ greatly from He*, especially in the liquid state, will scrv« to make possible further investigation's into the many questions tluft have arise» in connection with the low-temperature characteristics of helium. Further,, it ha.s been observed in the course of these experiments, designed to studVy th.e mechano-caloric -effect in helium 1 1 , t h a t temperature differences of the order o f 10 "*2 could be obtained by mechanically altering the relative height o f the liquids in the two containers, "thus xnakir&g possible an exact measurement of tfcie entropy of super-fluid helium II. The Ohio State group which is workiog under contract with the Office o f Navel Research included J. G. Daunt, R. E . Probst, and H. L. Johnston.. A. O . Ni^r and L. T. Aldrich of the University of Minnesota also collaborated.
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