VOLUME
13A
2 4, N O . 7, J U L Y 1 9 5 2
the analyst's column V \ / T E I G 1 I T S and weighing are so funda' ^ mental to all analytical operations that every analyst is interested in any contemplated changes, especially if such changes are being considered b y the National Bureau of Standards. At the meeting of the Scientific Apparatus Makers Association a t Chicago on May 7, considerable discussion took place con cerning specifications for mass standards and other weights; a summary of the remarks follows: Specifications for various classes of weights were thoroughly re-examined in connection with the revision of the 1918 National Bureau of Standards Circular No. 3, "Design and Test of Standards of Mass." Weights may be divided into four groups according to their use: the scientific standards group, the commercial standards group, the rough laboratory group, and the trade group. T h e scientific stand ards group includes the reference and working standards used in scientific and technical laboratories. The commercial standards group includes the standard and test weights used by state and city weights and measures offices. T h e rough laboratory group includes the weights used for the less precise work of the com mercial and student laboratories. The trade group includes weights used in the purchase and sale of goods by the Govern ment and in ordinary trade.
Precision grade at half the cost
mi $4.95 each The Ultramax Buret is graduated to Bureau of Stand ards specifications for volumetric glassware of precision grade. This accuracy is assured by Precision Bore "Pyrex" glass tubing with inside diameter held to ±0.0003". The unique "Teflon" valve plug requires no lubricant of any kind, turns smoothly even after long and con tinuous service. Low surface friction prevents "freez ing." The valve body is part of the precision bore tube, so the surface is glazed, not ground. Hex nut and knurled locknut provide positive turning, permit independent pressure adjustment and prevent plug from slipping out. The glass tip is replaceable. The Ultramax Buret is easy to clean and re-assemble. Test it yourself in your own laboratory. Available from stock at laboratory supply dealers,or direct from factory. *With automatic zero, $11.00 each. Prices quoted are for 50 ml size in case lots of six.
Only the scientific standards group and the rough laboratory group were con sidered a t the SAMA meeting. T h e recommended changes: 1. Inclusion of the recently introduced class of microbalance weights 2. Introduction of "group" as well as "individual" tolerances on weights of a set of Classes M and S 3. Use of tighter tolerances for new and newly adjusted weights, particularly. Class S, as compared with maintenance tolerances for these wreights 4. Introduction of a new Class S2 to fill the gap between Class S and the old Class S2 5. Increased specifications as to smooth surface, clean edges, nonvariable adjusting material, and everything that avoids variability in weights The new Class J standards are intended for use in calibrating quartz-fiber and other microbalances. T h e tolerance of 0.0030 mg. has been selected to permit the National Bureau of Standards to calibrate these weights to 0.0001 mg. With any larger tolerance extra small weights would have t o be introduced into the tests, and these would double the uncertainty. {Continued on paye 15 A)
FISCHER & PORTER COMPANY 9 7 0 County Line Road, Hatboro, Penna.
Please ship Ultramax Burets at $ Please ship Automatic zero a t $ Please send literature Π NAME
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