RESEARCH
New Text
Excellent for micro techniques. Supports up t o 5 lbs. with precision control of vertical adjust* ments thru an elevation of more than 3*. 3x3* stainless top and bottom aux* iliary plates for quick attachment. $18.75.
cenco
the most complete line of scientific instrument and lab· oratory supplies i n the world.
CENTRAL SCIENTIFIC CO.
Another Look at Glass A n e w concept o f glass struc ture is b a s e d on a structural unit—the "vitron" tiiLsivNT day thinking on the struc ture of matter in the glassv state max haxe to he rex ised if a nexx hx pothesis from the» National Bureau of Standards is corrohorated. Λ nexx concept of glass structure, bused on a structur.il unit tailed the "vitron.** states that glass is a noiicrx st.dline sxstematic ar rangement of atoms oxer submicroscopic xolumes. L. \ \ . Tiltoii. xx ho suggests the nexx concept. v axs the vitron is a submicroscopic duster of pentagonal dodecahedru with subuiiits of sihcon-o\x gen tetrahedra. The clusters are joined together looselx bx xx hat Tiltoii calls "connective tissues*' that bax e weaker bonds hut greater densities than the χ itrnn. Todav. scientists* theories of glass
structure χ iexx the atomic arrangement and interatomic distances of nearest neighbors in a glass and its most closely related crxstul. crystohalite, as being similar. But in glass, the many slight irregularities introduce a randomness that masks the periochcitv characteristic of crxstals. Tiltoii points out. I'nder the vitron concept, glasses and crxstals would differ more rutid.imentallx because of the difference in their structural sx uunctrics. Thcoreticallx . Tiltoii sax s. crxstals can grow indefinite!) Λ ithout stress, but the vi tron is aiitomatii alb limited in growth because of ever increasing distortianal stresses This nexx concept developed Irani observations of the reversible volume changes in silica glass produced bv an nealings at different temperatures Ac cording to the vitron concept, these volume changes are caused by a tempeiature-sensitivitv of the hond angles. Present theories attribute the changes to bond stretching, breaking, or re forming.
1710 Irving P o r k Rood · Chicago 1 3 / Illinois Bronchos a n d Warehouse·—Mountainside, N. J. Boston · Birmingham · Santa Clara · Los Angeles · Tulsa Houston · Toronto · Montreal · Vancouver · Ottawa
ADSORBENTS DILUENTS Floridin natural-mineral ad sorbents are successfully being used for applications in adsorptive refining, filtration, neutralization, decolorization, dehydration, polymerization, catalysis, diluents, insecticide carriers, filters, binders, clean ers, and many others. If your laboratory or pro duction processes can use an economical, efficient, natural material for these or similar uses, it will pay t o investigate. Write today.
FLORIDIN COMPANY ADSORBENTS Oept. 8.
56
P.O. Box 9 8 9
C&EN
NOV.
m
Tallahassee, Florida
10,
1958
This off-axis view of a four-element vitron has four slightly deformed dodecahedra. The coiled wire springs indicate extra O-charges; the vacant tetrahedral corners are Si "»" charges where other vitron» attach by oxygen bridges
Organic chemists *
&
>
•
•
*
·
.
.
'
•
'
'
•
*
'
•
'
•
• • • "
»
.
*
·
.
•
•
• • ' •
.
-
•
•
•
•
•
•
•
•
·
•
-
. ·
LÉSÉES,
'••
ë^i^çreiajii , J:,.:-L.:;*; ,..::_·
L_',..... ....:',•...,;;.-..·;;.;ν.,..
ι"...::'...:·;:..::,.·it/;.£.;: :.Ar2NH
WHY THIS INTEREST?—Because o f t h e a b i l i t y of l i t h i u m a l u m i n u m h y d r i d e t o act a s a p o w e r f u l r e d u c i n g a g e n t f o r o r g a n i c compounds. Unlike many intermediates. L A H avoids side reactions, polymerizations, condensations and cleavage. E v e n m o s t hindered c o m p o u n d s can be successfully reduced with LAH. WHAT ARE THE MOST SIGNIFICANT FACTORS?—LAH is s e l e c t i v e . It can p r e f e r e n t i a l l y r e d u c e e s t e r s in t h e p r e s e n c e o f n i t r o g r o u p s . It a l s o r e a c t s w i t h c o m p o u n d s c o n t a i n i n g a c t i v e H , liberating H _ T h e H . c a n b e m e a s u r e d e a s i l y , g i v i n g a q u a n t i t a t i v e d e t e r m i n a t i o n o f a c t i v e H-. I n t h e r e d u c t i o n o f functional groups, m e a s u r e m e n t o f t h e amount o f reagent c o n s u m e d p e r m i t s d e t e r m i n a t i o n of r e a c t i v e f u n c t i o n a l groups; acids, ketones, esters, aldehydes, anhydrides, a m i d e s and nitriles. HOW ABOUT SOLUBILITY?—LAH i s s o l u b l e i n d i e t h y l e t h e r a n d t e t r a h y d r o f uran. IS IT EASY AND SAFE TO USE?—LAH r e a c t s s w i f t l y , s u r e l y w i t h s t a n d a r d t e c h n i q u e s in c o n v e n t i o n a l e q u i p m e n t . R e d u c t i o n s can b e carried o u t at room temperature a n d atmosphere. R e d u c t i o n t e m p e r a t u r e s r a n g e f r o m — 8 0 ° C t o -f-100°C, depending upon t h e solvent used. WHAT ARE SOME TYPICAL REACTIONS?—Here i s a partial list o f r e a c t i o n s w h i c h h a v e p r o v e n of w i d e i n t e r e s t :
LLAIH4
Reduction of Aromatic Nitro Ester: o C
CH2OH
-OC2H5
LiAlH
I NO* Reduction Aliphatic Nitro Esters:
NO*
Ο LiAlH« CH a CH-(CH2)2C - OMe > CH,CH(CH*)3OH NO:
NO*
Reduction Acetylenic Compounds: .OH =CH
-»•
76SS Yield •H. Feuer T . Xucera JACS 77.5740 (195S)
.OH
LiAlH
* -C=C-H / J. dioxanee \ u Journal
Reductions of Fluoro Ester:
E. B. Bates, E. R . Joaes of the ChemicaJ Society JACS 1854-eO (1954)
L1AIH4
CFaCFaC - O E t
-> CFaCFaCH^OH
W e welcome you t o w r i t e for Data Sheet No. 401D, and for answers to your specific questions about Lithium Aluminum Hydride. r—ι
CHEMICAL· H Y D R I D E
TEL Metal Hydrides Ι ΜI ΠΙΟ
CONGRESS
DIVISION
Incorporated
PIONEERS IN HYDROGEN COMPOUNDS STREET,
BEVERLY.
MASSACHUSETTS NOV.
10. 1 9 5 8 C i E N
57
2 56
2.54μ
2.58
2.60
2.62
2.64
RESEARCH
Polyester Tags Fatty Acids
FUNDAMENTAL OH STRETCHING WATER BANDS RANGE: 2.50-2.65 microns
RESOLUTION: 1 cm1 (6Â)
The above curve illustrates the high resolution that users of Cary Model 14 Spectrophotometers are getting for measurements in the near-IR region. The Model 14's ability to resolve such fine structure is a feature not ordinarily found in a general purpose instrument having a wide wavelength range (1860 A-2.65 microns). In most of the ultraviolet-visible region, resolving power of the Model 14 is better than 1À. High resolving power is just one of many features that make the Model 14 so useful. A broad wavelength range, a wide choice of scanning and chart speeds, accommodation of a variety of types and sizes of sample cells, stray light of less than 1 ppm, photometric reproducibility better than .004 in absorbance even at high absorbance, and many special accessories suit the Model 14 to a wide variety of spectror^hotometric problems requiring fast, accurate analyses. These and other performance features have made it the preferred recording spectrophotometer of leading research laboratories throughout the world.
Details of these benefits and complete specifications on t h e Model 14 are yours for t h e asking. Write f o r Data File C 12-118.
New Text APPLIED
58
PHYSICS
C&EN
NOV.
CORPORATION
10,
1958
2724
SOUTH
PECK
ROAD
MONROVIA,
CALIFORNIA
Λ stud> of a variety of polyesters s> nthcsi/cd from dibasic acids and pokgheols has shown that one of these—the polyester of succinic acid and 1 4-butanediol —is particularly ef fective as the liquid phase in gas-liquid chromatographx of fats and oils. Us ing this polyester should permit more accurate separation of saturated and unsaturated acids in the analysis of vegetable oils, sav s Β. M. Craig of Canada's National Research Council. This pol\ ester, with a melting point of Wi C . has 10 times the heat stabilit\ of Λ\\\ other commercially available poh ester suitable for this purpose, Craig and his associates say. In anah/.ing the fatty acid composi tion of various vegetable oils. Craig and coworkers used a succinate-butanecliol column operated at 215 C. This col umn. 6 feet long and ' , inch in diam eter, was packed with 40- to SO-mesh ('elite treated with 30' «· by weight of the poh ester. The sample was passed into the column b\ a stream of helium flowing at 60 ml. per minute. This setup permits improved separation of stearic, oleic, and other fatty acids. ( .as-liquid chromatography permits difficult samples to be analyzed accu rately and. at the same time, makes it possible to run analyses on unusually small samples. Determining the total amount of unsaturation of a fatty acid by measuring its iodine value might re quire 100 to 300 mg. of the material. For analysis b\ gas-liquid chroma tography onk 1 to 5 mg. might be needed. In addition, the method can be used to measure separately the saturated and unsaturated compounds. The gas-liquid chromatographic method has been improved by use of thermal conductivity detectors and by converting the oils to their esters. The chain length of the sample can be found by using silicone columns; satu rated and unsaturated materials can be separated by columns of polyesters. Determinations by gas-liquid chro matography can be more accurate than those based on iodine values and spec tral methods. Craig told the meeting of the American Oil Chemists' Society in Chicago. This was shown by using synthetic samples of known concentra tion resembling such vegetable oils as sovbean and linseed oils. _
