INDUSTRIAL
470
of physicists. T h e work reviewed in t h e s e columns last year on nuclear transformations has been continued. Literally hundreds of nuclear ' ' r e a c t i o n s " are now known, in the course of which the nuclei of elements are changed to those of o t h e r elements or other isotopes of t h e s a m e element. These changes m a y be caused by t h e incidence of alpha-particles, protons, deuterons, o r neutrons (and possibly other rays) a n d give rise in t u r n to rays of all these types. Artificial R a d i o a c t i v i t y Some of t h e product nuclei are isotopes not before found occurring in n a t u r e . There are cases in which the same product can be formed in more than one w a y . M a n y of t h e new isotopes formed are unstable and shortly break down into stable known elements by t h e emission of an electron or a positron. This is t h e phenomenon of "artificial" or " i n d u c e d " radioactivity. Attempts are being made to increase the "yield" of artificial radioactivity to t h e point of competition with naturally occurring radium and its products. It appears likely t h a t the effort will be successful. It is necessary to select an artificial radio element which decays slowly enough for practical purposes (halflife a matter of hours r a t h e r than minutes or less) and yet not so slowly t h a t its radiations are too weak. It must also be one which can be produced relatively easily by a nuclear reaction. T h e most promising k n o w n reaction is t h a t between bombarding deuterons of several million volts energy a n d sodium ( D 2 + Na" > - H l + nNa 2 4 ). The product radiates electrons and decays with a halflife of 15.5 hours ( N a " >• e + 2 2Mg ). Radio-sodium is also produced by o t h e r reactions which involve neutrons—e. g.: nNa" + oni I , M R " + 0n» „AI» + on»
>. „ N a M > ,Hi + „Na24 >- 2 H e 4 + nNa*«
These reactions a n d t h e fact t h a t they are known illustrate the progress made in the field in a very short t i m e . I t has been possible to verify the Einstein law of the equivalence of mass a n d energy (E = mc 2 ). Nuclear reactions use t h e energy of motion of bombarding particles and of mass lost during t h e reactions. T h e total mass a n d energy m u s t be equal for each member of the reaction equation. Certain reactions were observed which seemed not only to d e p a r t from this law of conservation b u t to result in an increase of energy-plus-mass. These have led t o a slight revision of isotopic weights, since confirmed b y Aston with an improved mass spectrograph. Neutrons ordinarily penetrate m a t t e r much more readily t h a n any other particles or rays of comparable energy. T h e y are absorbed more by layers of paraffin, water, or other hydrogen-containing m a t e rials than b y lead. This phenomenon has been explained through the fact t h a t neutrons make a p p a r e n t l y elastic collisions with hydrogen nuclei and give u p a large part of their energy a t each encounter. It has been shown t h a t neutrons may b a t a r o u n d in paraffin until t h e y come into t h e r m a l equilibrium with t h e molecules. N e u t r o n s , so slowed down, no longer pass readily through m a t t e r , b u t are absorbed, probably by being c a p tured into t h e nuclei present. T h e power of absorbing slow neutrons varies m a r k edly among t h e elements, being so great in the case of c a d m i u m t h a t this element can be used as a shield for slow neutron rays.
AND
ENGINEERING
CHEMISTRY
It i s significant t h a t the Nobel prizes for physics a n d chemistry for 1935 were both awarded for work in these fields. The discovery of t h e neutron was credited to J a m e s Chadwick, winner of t h e physics prize, and t h a t of induced radioactivity to Frederick Joliot a n d his wife, Irene JoliotCurie, winners of t h e chemistry prize. Cosmic Rays Cosmic rays have been investigated as actively in 1935 a s in 1934, t h r o u g h worldwide surveys and pilot balloon ascensions using self-recording instruments, and recently during t h e stratosphere flight of C a p t a i n s Anderson a n d S t e v e n s . M u c h new a n d precise work has also been done in laboratories with counters a n d with cloud chambers in magnetic fields. W h a t ever t h e primary cosmic r a y s m a y be, t h e latter instruments show t h a t they are accompanied by showers of positive and negative electrons. T h e formulation of dependable theories regarding t h e n a t u r e
VOL. 13, N O . 2 4
a n d source of t h e rays is awaiting t h e stepby-step accumulation of accurate data a n d t h e separation of t h e numerous effects from one a n o t h e r . Atomic Spectra Among other fields m a n y i m p o r t a n t researches have been carried o u t . An example is the extension b y P . W. Bridgm a n of his studies of m a t t e r u n d e r very high pressure. A n u m b e r of new phases have been produced with increased pressures plus mechanical shear. T w o forms of ice produced are s t a b l e enough t o remove from the pressure a p p a r a t u s and examine with x-rays by t h e powder method. A new comprehensive s u r v e y of atomic spectra is being m a d e by G. R . Harrison, using a machine which a u t o matically measures s p e c t r u m plates recording wave lengths to eight characteristic figures and also line intensities. T h e machine has a capacity of 600 lines an hour.
Thirtieth Anniversary o f Laminated Safety Glass Marked by General Use in A u t o m o b i l e s P a u l D. B o o n e , R o o m 4708, U. S . P a t e n t Office, W a s h i n g t o n , D. C . TISa bit h a z a r d o u s to single o u t a defin i t e person a n d unequivocally s t a t e that h e invented some broad basic idea, for, a l t h o u g h the best records available may so indicate, there is nevertheless t h e possibility of plant use to a limited extent of which no records were' kept. B u t J o h n Crewe Wood, of Swindon, England, would seem t o be t h e person to whom t h e honor belongs of inventing laminated safety glass, for in December, 1905 a British p a t e n t , No. 9972, issued, entitled " I m provement i n Glass Screen Windows for M o t o r Cars." British p a t e n t s a t t h a t time gave t h e occupation of inventors a n d , s t r a n g e as it m a y seem, Wood w a s a solicitor o r lawyer. His description is both clear a n d interesting, reading in p a r t : To t h e above end my invention consists in providing two sheets of glass between which is fixed or cemented a sheet of film of any transparent adhesive substance or material with sufficient elasticity to prevent splintering of the parts; for example, I employ a sheet of celluloid between two sheets of glass o r a film of gelatine less brittle than glass a n d not liable to splinter.
I
Canadian balsam a n d sodium silicate were mentioned a s cements or adhesives. The non-splintering a n d greater strength characteristics of laminated glass have decreased the h a z a r d s of motoring, especially a t h i g h speed. Wood stressed t h i s in his original patent, b u t it took years before t h e public and manufacturers really appreciated i t s possibilities. In 1914 it began to achieve some commercial significance. T h e lenses in gas masks, goggles, a n d other e q u i p m e n t of t h e forces a t war were equipped w i t h safety glass. Then when automobiles, which prior t o 1919 were of t h e open design, changed to t h e closed t y p e the trend became inevitable in t h e interest of safety. There were m a n y problems which beset t h e manufacturers, such as discoloration of t h e layer between t h e glass, t h e tendency of the g l a s s to " l e t - g o " t h e plastic, and t h e cost of manufacture. T h e development of laminated glass can be followed by consulting t h e patents issued b y the U. S. P a t e n t Office, under t h e designation "glass u n i t i n g . " In t h e years prior t o 1028 only 14 p a t e n t s h a d been issued and o f these 10 were g r a n t e d to private inventors. T h e n m a r k e d acceleration i n their issuance followed and t h e efforts of some of t h e well-equipped cor-
poration research laboratories became evident. In 1928 t o date, 154 p a t e n t s , all but 21 of which were assigned to corporations, were issued. It is beyond the scope of this article to enumerate t h e various contributions or t o appraise t h e m , but some of the more recent will be sketched in part. T h e laminae h a v e been united direct t o one a n o t h e r by polymers of vinylethinyl carbinol, ethyl ester of acrylic acid, condensation product of maleic acid, a n d 1,3glycols. I m p r o v e m e n t s have been m a d e in uniting t h e plastics to t h e glass a n d a m o n g t h e bonding agents boric acid, in conjunction with silicic acid, find uses. Oxycellulose a c e t a t e for uniting glass to ester plastics is suggested. One p a t e n t of interest in connection with the modern t r e n d of streamlines is t h a t for uniting or forming curved laminated glass. A sheet of galvanized iron is placed between glass sheets. When t h e glass is at t h e proper temperature, heat and pressure are applied t o bend t h e glass. The metal is then removed and t h e spaced glass is bonded with a plastic layer. Credit is due John C. Wood for his invention in 1905, but praise m u s t be given for its perfection to the chemists since 1921 who have made i t a real success, a n d t o the companies providing t h e m with e q u i p m e n t unknown t o Wood and Benedictus, t h e two pioneers.
Miniature Glass Plant M I N I A T U R E glass p l a n t has j u s t been completed in the laboratories of t h e Bausch & L o m b Optical Co., Rochester, N. Y., a t a cost of $8000, a n d will tour m a n y of t h e larger cities of t h e United States a n d be shown a t scientific g a t h e r ings, industrial conventions, a n d m u s e u m s . T h e model, which took a year a n d a half t o build, consists of a b a t t e r y of t h r e e glassmelting furnaces, raw material storage bins, mixers, a n n e a l i n g ovens, casting table, a n d cutting rooms in operation, with small electric t r u c k s , m a n n e d b y miniature operators, transferring t h e molten glass from t h e furnaces to t h e casting table, where it is automatically rolled into sheets a n d conveyed into t h e ovens. An a u t o m a t i c film balopticon, synchronized with the operations of t h e model, projects the s t o r y of each operation on a screen a t t h e t o p of t h e model while t h e operation is t a k i n g place.
A
