Standards grades/grade requirements

A 0.4512-g sample of primary-standard-grade Na2C03 required 36.44 luL of an H2SO4 solution to reach the end point in the reaction... 

One unit of bacitracin USP is defined as the activity given by 26 micrograms of the dried FDA master standard. The USP requirement for commercial bacitracin is a potency of at least 40 units per milligram in a bioassay with Micrococcusflavus or Sarcina lutea. Pure bacitracin A has a potency of about 100 units per milligram. Standards for animal feed grades of bacitracin are available (71,81,82) as are analytical methods (67). 

Grade A is the highest standard, and is required for local zones where high-risk tasks are carried out. Examples are the aseptic filling of a product following filtration through a 0.22 pm filter to render it sterile, and general aseptic manipulations. This is usually achieved by the use of cabinets or hoods that enable laminar airfiow patterns to be established. 

EC grade C is the closest classification to Federal Standard grade M5.5 (FS209E). In both cases, the limits specified are guidelines only and not regulatory requirements. 

Dry casein (acid) that fails to meet the requirements of U.S. standard grade, or contains Salmonella or coagulase-positive staphylococci, is considered unsuitable for human food and is not assigned a U.S. grade. 

Again, in considering the price to be paid for paper, it is vital that the correct comparisons are made. If a standard commodity grade of neutral/alkaline sized paper, made in large tonnages, meets the required specification for permanence, it should clearly cost no more than the corresponding acid sized paper. Even if it does not meet a set permanence specification, it is very likely to be considerably better in this respect than the acid sized grade it has replaced. 

The titrant, TnBAH solution, requires standardization at least twice daily when in use over an 8-h period. Duplicate samples of primary standard grade benzoic acid are weighed into the titration vessel and 60 ml of DMF (N,N -dimethylformamide) is added. The glass and TnBACl-filled calomel electrodes... 

The tube, about half filled with molten TNT, was stoppered, removed from the bath and vigorously shaken 5 times at the rate of one shake per 2 secs. The tube with contents was immediately placed in a thermostatic bath maintained at 86 1°. The end point of frothing (duration of foam) was recorded as the time in seconds required for the froth to break until only 3 bubbles remained. The approximate amt of froth was also noted. Some standard grades of TNT showed duration of frothing as low as 50 secs, while TNT with abnormal frothing recorded 164 secs before addn of surface-active agents and as low as 59 secs after the addn... 

Starch, as ordinarily prepared either in the laboratory or commercially, requires very little additional purification. It is one of the few natural organic substances that can be obtained readily in a high state of purity. A typical analysis of a standard grade of commercial corn starch shows that it contains, on a dry basis, approximately 99.0% starch, 0.05-0.07% nitrogen, 0.02% phosphorus, 0.08-0.10% ash, and 0.5-1.0% fatty substance. Normally, the starch contains 10-12% moisture. The fatty material and a part of the phosphorus can be removed by extraction with 85% methanol - - or by extraction with ethanol containing a small amount of nitric acid, although the latter treatment may cause some degradation of the starch. 

Air grading is little practiced today. At one time it was a standard method for preparing sandpaper gradings. It requires large and costly settlement chambers. It is impossible to prevent eddying currents due to variations in the blast and frictional contact with the sides of the expansion chamber. It would be possible to produce uniformity in the velocity of the air currents by the use of gratings as is done in the air tunnels for aviation experimental work did not such gratings interfere with settlement. 

Archer KJ (1985) Bacterial modification of Douglas fir roundwood permeability. PhD thesis. University of Canterbury, Christchurch, New Zealand Archer RR (1986) Growth stresses and strains in trees. Springer-Verlag, Berlin AS/NZ (1997) Timber stress-graded product requirements for mechanical stress-graded timber. AS/NZS 1748. Australian/New Zealand Standard Ashworth JC (1977) The mathematical simulation of the batch-drying of softwood timber. 

ECS (1995) Structural timber grading-requirements for visual strength grading standards. 

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