Nitrogen grades available

Table 1. Nitrogen Grades Available. (Units in ppm (mole/mole) unless otherwise shown)... 

A. Sources. In the United States high-pressure compressed nitrogen is available in several purity grades. For example, the Matheson Company sells... 

This is supplied as an azeotrope with water (constant boiling hydriodic add), b.p. 125.5-126.5 °C/760mmHg, d 1.70, which contains 55-57 per cent w/w HI (0.936 to 0.99 g HI per ml). Additional grades available contain 45 per cent w/w HI and 67 per cent w/w HI the latter is stabilised by the addition of 0.03 percent w/w of hypophosphorous acid. Once a bottle is opened the contents tend to deteriorate, becoming discoloured in a few days. This can be avoided by purging the container with nitrogen before resealing. 

Grade Available as 98% pure, supphed under nitrogen atmosphere, and as 55% solution in hydrocarbon. 

Quartz-distilled water was used throughout the work. Sodium acetate (Suprapur) and potassium peroxodisulfate (pro analysi) were products of Merck and were used as received. Polyoxyethylene(23)dodecanol (Brij-35) and polycyclic aromatic hydrocarbons were purchased from Aldrich and used without further puriflcation. A 0.010 M stock solution of 9,10-diphenyl-anthracene was prepared in ethanol and Wcis daily diluted to an appropriate concentration in the eluent. Nitrogen was of the purest grade available. 

The legal basis for the sale of fertilizers throughout the world is laboratory evaluation of content as available nitrogen, phosphorus, and potassium. By convention, numerical expression of the available nutrient content of a fertilizer is by three successive numbers that represent the percent available of N, P20, and K O, respectively. Thus, for example, a 20—10—5 fertilizer contains available nitrogen in the amount of 20% by weight of N, available phosphoms in amount equivalent to 10% of P2O5, and available potassium in amount equivalent to 5% K O. The numerical expression of these three numbers is commonly referred to as the analysis or grade of the fertilizer. Accepted procedures for laboratory analysis are fixed by laws that vary somewhat from country to country. 

In the last decade there has been increased interest in the ferritic steels stimulated originally by the availability of new steel-making processes which gave hope that the brittleness problem could be solved by suitable control of carbon and nitrogen contents. This hope has only been partially realised, but as a result a number of new grades have been marketed which do represent useful additions to the range. These have became known collectively as Super Ferrities . Some examples are in Table 3.12. A substantial amount of relevant information was presented at the conference indicated in Reference 5. 

Commercially available potassium superoxide and tetramethylammonium hydroxide pentahydrate from Aldrich were used as supplied without further purification. Industrial-grade nitrogen gas does not require any further purification, but the ammonia gas, 99.999%, should be at a minimum purged through Drierite before use. AU work is done under a nitrogen flow unless otherwise stated. 

Chloroprene is available commercially on a restricted basis in the United States as crude P-chloroprene with a minimum purity of 95% (Lewis, 1993 DuPont Dow Elastomers, 1997). The principal impurities are dichlorobutene and solvents, with smaller amounts of 1-chlorobutadiene (a-chloroprene), chlorobutenes and dimers of both chloroprene and butadiene. Due to its reactivity, chloroprene is stored at 0°C or below under nitrogen and contains significant quantities of inhibitors, such as phenothiazine, tert-butylcatechol, picric acid and the ammonium salt of A -nitroso-N-phenylhydroxy lamine, to prevent degradation and polymerization (Stewart, 1993). Generally within six weeks of manufacture, crude chloroprene is distilled to produce polymerization grade, which is used within approximately 24 h of distillation. 

Dimethylsulfoxide is purified by filtration through a 2 x 25 cm chromatographic column filled with alumina (activated grade I, neutral, 150 mesh), under a nitrogen atmosphere. This procedure of purification of the solvent is crucial to obtain the indicated yield, since on use of distilled or commercially available anhydrous dimethylsulfoxide, extensive decomposition takes place. 

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