EDITOR'S COLUMN procedure performed in a s t a n d ardization l a b o r a t o r y and should include date of calibration, n a m e of operator, identification of the reference s t a n d a r d used, and a de tailed record of observations and computations made. This t y p e of record,, when audited, will disclose the adequacy of equipment and procedures used and will therefore constitute evidence of the validity of the derived values. Lee C a h n of the C a h n I n s t r u ment Co. described the effects of aerodynamic disturbances on a new 2.5 g r a m electrobalance (used for making measurements in vacuum a t normal or reduced atmospheres), and methods for achieving repro ducibility with this balance. Lloyd B. M a c u r d y , recently retired from the Bureau, described the violent and erratic changes t h a t occur in the indication of a balance a t near isothermal conditions and when the top of the balance case is cooler t h a n the bottom. H e also suggested practical methods for minimizing these effects, and de scribed experiments with several insulation configurations which controlled these t h e r m a l disturb ances. H. A. B o w m a n of the B u r e a u showed d a t a t a k e n on the N B S ex perimental one-kilogram balance, in which the sources of arrestment errors associated with the coupling between the suspension and the beam were reduced to a few p a r t s of 10 9 . This was done by a design in which the knives and flats were maintained a t a constant load throughout the entire arrestment and weighing cycle and by a multi ple link suspension. Mr. P o n t i u s developed m a t h e matical formulas to show the cumu lative effects of various systematic and r a n d o m errors t h a t m a y occur in balance performance. D r . Churchill Eisenhart, chief of the B u r e a u ' s statistical engineering laboratory, reminded the audience t h a t " a c c u r a c y " refers to the close ness to the true value, while " p r e cision" refers to the closeness of re peated measurements.
ίϊοοΜΓ
ALBERENE
for 75 years the only perma nently satisfactory material for chemical laboratory table tops, shelving, sinks, splash backs, drain boards and fume hoods. Prompt delivery. ALBERENE S T O N E - A DIVISION OF THE GEORGI/> M A R B L E COMPANY. For FREE l i t e r a t u r e and t e c h n i c a l assistance address: THE ALBERMAR COMPANY, 386 PARK AVE. SOUTH, NEW YORK 16, N. Y., DEPT. C.
STONE
Circle No. 9 on Readers' Service Card
New PHOENIX
AMINO ACID ANALYZER Model K-8000 Automatic Analysis of A m i n o Compounds in • Protein Hydrolysates • Protein-free p l a s m a a n d other • Physiological fluids • Tissue extracts • Hydroponic solutions •
Foods
• Culture m e d i a •
Pharmaceuticals
• A d a p t a b l e to Phoenix Stream Splitting System 5 5 0 0
Sensitivity: 0.1 t o 3.0 micromoles of amino acid with a precision of 1 0 0 zL· 3 % . Use ful results at even lower levels.
PPI
PHOENIX PRECISION I N S T R U M E N T COMPANY 3803-05 NORTH FIFTH ST., PHILADELPHIA 40, PA. Circle No. 144 on Readers' Service Card VOL. 3 4 , N O . 1 1 , OCTOBER 1 9 6 2
·
91 A
