EQUIPMENT Weigh W a y Down Torsion microbalance is sensitive to twentieth of one microgram over w i d e temperature r a n g e A
N E W MICROBALANCE, c l a i m e d to b e
capable of weighing small samples quickly and m u c h more accurately than any other balance today, is n o w being used in fundamental research.. The balance combines extreme sensi tivity—one twentieth of a microgram— with a design rugged enough to per mit portability and use by unskilled hands. The n e w instrument is of the "nullzero" torsion type. It is, in effect, a static balance—in contrast to the com mon displacement-type analytical bal ance. It is designed to accommodate unusually large differences in weight; an electromagnetic restoring force maintains zero-point position. Deflec tions are read b y optical beam, a n d control of coil current permits measure ment of very small weight changes.
This design w a s originated at Bristol University, in England, by Ph.D. can didate T. J. Jennings—now research fellow at Alfred University. Recent development w i t h T. J. Gray, profes sor of physical chemistry at Alfred, has l e d to a light b u t rigid girder-beam construction of fused silica. The bal ance is degassed by heating to 450° Ct in' vacuum. With ion-bombardment degassing (at 250° C. i n helium), tungsten fibers sealed with silver chlo ride can b e used in the assembly. These provide substantially the same sensitivity ( 5 Χ 10"8 gm.) as the silica fibers. • Rugged Construction. The beam is fabricated from fused silica rod (0.5 to 1.0 mm. diameter). Either drawn silica or tungsten fibers serve as main supports and beam-end fulcrums.
T. J. Gray (left) and codeveloper T . J. Jennings make and sell their submicrobalances as a paying hobby. N o w that they have settled on a design, they can turn one out in a few hours. Here, Gray watches Jennings make a n adjustment
The balance is designed to retain h i g h sensitivity but at the same time b e able to withstand being moved a n d used by unskilled hands. Here, Gray's hand holds balance in its transit c a s e Tungsten-fiber construction gives greater load-carrying capacity. On t h e other hand, all-silica balances can b e improved to offer a little greater sen sitivity ( 5 Χ 10"9 g m . at a reduced load of 0.25 gm.), says Gray, but 10' 7 g m . is t h e practical limit anyway. Buoy ancy,, thermonuclear flow, and other effeët4 cannot be corrected beyond this level, h e observes. A rod :of >-mëtal, set at 4 5 ° to t h e beam axis, is accurately centered relative to the support fiber. With this, a magnetic field generated i n H e l m holtz coils supplies a restoring torque. Thus the balance can be removed from its case without affecting calibration. • Instrumentation. Measurement of current in the Helmholtz coils is t h e present hmiting factor -with these microbalances. Precision potentiometers give absolute accuracy of 1 0 p.p.m. Incremental changes can be read more precisely, but are limited by the electronic current regulator with its longterm stability of 1 p.p.m. (somewhat better i n short-term). Gray has designed his own electronic control equipment, which can be made to record automatically. H e and Jennings are making balances as a hobby and selling them on die side. In some cases they supply control attachments with the balances: in other instances they furnish full details to permit local construction. ί Applications. These n e w microbalances have already been used exten sively in adsorption and desorption studies on catalyst materials. Also, they are said to b e ideal for magnetic susceptibility measurements on single crystals. There i s no limitation on t h e balance and its attached pans beyond load, buoyancy effects, and thermo nuclear flow. The ability to manage a w i d e range of loadings is particularly useful, Gray AUG.
2 6,
195 7 C& EN
79
CRUSHED VERSA M I D p o l y a m i d e resins chemicaii provide easier, m o r e c o n v e n i e n t h a n d l i n g
Another! Opportunity I
C r u s h e d V e r s a m i d polyamide resins can cut your costs ! They offer an easier, more convenient method of formulating your product. You can save time . . . • Dissolving Resins • Blending Resins • In P l a n t H a n d l i n g
Versamids are thermoplastic resins offering quick, hard-grip adhesion; high resistance to mechanical and thermal shock, aging; excellent resistance to water, grease and oils. They offer a wide range of
softening points and solubility; are compatible with many resins and plasticizers. Flexibility and high physical strength, coupled with great safety (they are non-toxic) make Versamid polyamide resins increasingly important to industry. Versamids 9 0 0 , 9 3 0 , 9 4 0 and 9 5 0 are available in the new crushed form, packaged in 50-lb. multi-wall paper bags . . . convenient to store and handle. Use them profitably in paper coatings, thixotropic paint, heat seal adhesives, printing inks, other industrial applications.
uet Mo*? tacts! bend tor additional înîormation on versamid polyamide resins. Write Department CES, Chemical Division, General Mills, Kankakee, Illinois.
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EQUIPMENT
explains, in studies of thermal decom position of solids and in oxidation or corrosion of metals. The balance op erates satisfactorily, h e says, from tem peratures below that of liquid nitrogen lo above 1800° C.
Grinding Labs Particle technology laboratories have been opened this month by Electro Metallurgical Co. and Karr & Co. Electromet plans to study both size re duction and enlargement of ores, while Karr will custom grind organic prod ucts on a service basis. Electromet's lab, at Niagara Falls, Ν. Υ., has crushing, grinding, and separating equipment, several types of furnaces and auxiliary equipment to study agglomeration of fines, and a pi lot scale fluid bed reactor for reaction studies. The Karr faculties, located at New Washington, Ohio, have a complete line of grinding and separating equip ment to make almost any size range of most organic chemicals.
^ O h m a r t has introduced a gage for measuring density, gravity, or per eent solids of materials from outside the vessel.
gamma specific process process Ε5
• Industrial Instruments has developed a battery p o w e r e d electrolytic conduc tivity recorder for u s e at locations where electricity is not available. Two 6-volt batteries supply power and should last for albout two months, ac cording to the company. Ε6
• Plastic a g i t a t o r s with blades u p to 10 ft. in diameter are now being mar keted by Haveg. Plastic protects the steel drive shaft. The agitators can be used with free-flowing liquids and thin sludges, the company says. * 8 • Nonskid cartons will be used in mar keting by Fisher Scientific as an aid to safety in t h e lab stockroom. T h e car tons have hundreds of liny welts in the paperboard tops and bottoms to hold stacks in place. Ε 9
Processing « · . • Pipe and fittings, developed by Resistoflex, have a lining of high density Teflon compouncl for corrosion resist ance. The pipe is available in sizes up to 4 in. Ε7
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Further useful information on keyed Equipment ifems men tioned is readily available . . . Use handy coupon on page 82 ψ
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August 12, 1 9 5 7
Readers Information Service Use this handy self mailer to o b t a i n further information or literature. Simply mark, clip coupon, fold, and mail Every week C&EN's editors survey a large volume of valuable scien tific, technical, and business information issued in the form of product announcements, booklets, catalogs, data sheets, etc. This material is digested and presented in several departments. For your conven ience this coupon is provided to facilitate requests for further informa tion o n these items as well as on products and services mentioned in advertisements.
• Button cell b a t t e r y , by Gulton Indus tries, is of sintered plate nickel-cad mium. The battery is about t h e size of a half dollar and comes in two rat ings—0.25 milliamp.-hr. a n d 0.5 milliamp.-hr. Ε1 • Label p a p e r , developed by Nashua for the textile industry, has new heatseal adhesive. T h e label paper does away with adhesive residue and paper splitting adhesion, according to the E2 company.
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CLIP C O U P O N — F o l d A l o n g T h i s L i n e — F a s t e n (Staple, T a p e , G l u e ) — M A I L
