Noremher, 1933
A N D
I N 1) il S'r It I A I.
15 N G I N E 1s R I N G
Typical results of exposure tests conducted on acetate and iiitrat.e laminations are shown in Figure 4; as can be seen, the lower half of tlic samples was protected during exposure. Sample A made with pyroxylin plastic decomposcd and separated a t the end of 767 hours of exposme. The average t,ime required for the decomposit,ionand separation of a number of similar nitrate laminations n-as 715 hours. Tlic breaking down of the nonbrittle portion of tlio nitrate 1aminat.ion evident in the photograpli results in a separation of the glassplastic surfaces and is undoubtedly due to the decomposition of the cellulose nitrate plastic caused by energy in the form of light and beat. Cellulose acetate plastic laminations made with tlre same kind of glass were exposed for 1000 hours undcr the same conditions and showed no evidence of decomposition of the plastic or separation of the laminations. A typical result of numerous such exposure tests on acetate laminations is sliown by Figure 4B. Thus the results of numerons tests clearly show that, with all other conditions comparable, the light stability of laminated safety glass made with cellulose acetate plastic is far superior to laminated glass made with cellulose nitrate plastic.
EFFECT OF
NEAT O X LAMIXATED SAFETY GLASSES
The stability of laminated safety glass towards energy in the form of heat is strictly dependent upon the heat stability of the plastic mst.cria1 nscd as the central portion of the composite structure. Owing t o tile much higher energy level of cellulose nitrate lis compared with cellulose acetate, cellulose nitrate plastic is considerably less stable to energy in the form of heat than
C €3 E M I S T R Y
1195
cellulose acetate plastic. The relative stability of these two cellulosic plastics towards lieat energy are readily demonstrated by their methods of working in the molding industries and also in the manufacture of safety glass. In the bonding operation of glass-plastic laminations, i t is customary that the glass-plastic sandwiches be subjected to the application of heat and pressure to effect the bonding. With the nitrate laminations, the laminating temperatures are limited to about 250" F. (121.1' C.); however, inthecase of the acetate laminations, temperatures as high as 350' F. (176.7" C.) may he satisfactorily used. If in the case of the nitrate laminations temperatures much above 250" F. are maintained for any great length of time, considerable decomposition ensues which is made manifest by the discoloration of the plastic to a brownish cast, due to the decomposition of the cellulose nitrate molecule with subsequent liberation of oxides of nitrogen. Also, the decomposition of cellnlose nit.rate isautocatalytic in nature. In contrast, cellulose acetate laminations may be maintained at laminating temperatures for fairly long periods without any apparent deleterious effect. One of the practical advantages of the greater stability of the cellulose acetate plastic towards heat is that it permits the use of temperatures snffcientlyhigh during the bonding operation to render the plastic fairly mobile, so that, when subjected to the proper pressures, the plastic is molded to remove any irregnlarities that might exist in the plastic surfaces; thus molding of the plastic sheet during the bonding operation results in a finished, laminated safety glass equal to plate glass in visual properties. RECPIIYSO July 27, 1933.
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The Alchymist by
THOXAY WYCK(WIJCE) (1617-1677)
This is one of a group of paintings by Wyck, all of which are of the same general style and type. I t is No. 35 in the series and is the second Wyck painting we have reproduced. the earlier one hsving been No. 5 in theseria. The original, of which this is a direct photograph, is in the Ducal Art Gallery in Braunachweig, Gormany. I t will he noted that the scene represents o combination study and lahoratory, showing a medieval still and other apparatus. All of Wyck's paintings show the draped curtains, atained-glass window, and the symbolic salamander, mually represented by a lizard, crocodile, or swordfish.
A complete list oi the first twenty-air reproductiona in the a d e & together with the detail8 fur obtaining 302 of the Maroh. 1933, issue. Addirional re photogrephie copier 01 the originals, w i l l 6 , found on produstions appear io earl, succeeding iaEUB, on pagep423.s82.844. 783.940, 1041.and 1138. Puichsse of these photographs does not confer any right. of pahIioation 01 theas iepiodutions. Special arranse ments nmd be made with Mr. Berolsheimer to obtain suoh rights.
