Commercial substances

The analytical reagent grade is suitable for most purposes. The commercial substance may be purifled by shaking for 3 hours with three portions of potassium permanganate solution (5 g. per litre), twice for 6 hours with mercury, and Anally with a solution of mercuric sulphate (2-5 g. per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65°. The pure compound boils at 46-5°/760 mm. 

Methylene chloride. The commercial substance is purified by washing with 5 per cent, sodium carbonate solution, followed by water, dried over anhydrous calcium chloride, and then fractionated. The fraction, b.p. 40-41°, is collected. 

Dioxan (1 4-dioxan diethylene dioxide). The commercial substance usually contains small quantities of acetaldehyde, appreciable... 

A study of the inventory list of 55,000 commercial substances shows that less than 10% of them account for 99.5% of production. A panel of authorities could provide a qualitative ranking of risk uncertainties which could narrow the list of substances to those of most immediate concern. 

The magnitude of the number of commercial substances (55,000) and the limited resources available to examine the potential risks posed by this large number of substances require that we understand the universe of chemicals we are considering so that guidelines for priority setting can be established. 

It is apparent from this discussion that if one narrows down the large universe of commercial chemicals to those produced in sufficient quantities, such that they might be expected to pose a possible health or unwarranted threat, there is a significant amount of information known about these substances or studies are being considered for a number of them. This is not to say that there is no need for continued testing of existing commercial substances, but the picture is not as bleak as some would want us to believe. 

In 1979 the sixth amendment to the dangerous substances directive (79/831/ EEC) introduced a notification system for new substances and made provision for the publication of an inventory of existing substances, the latter being those substances on the European market by 18 September 1981. The European Inventory of Existing Commercial Substances (EINECS) was published in 1990 and lists 100,106 substances (SLIM, 1999). A decade later some 30,000 or so of these substances were thought to be marketed in volumes of above 1 tonne per year, these accounting for more than 99 per cent of the total volume of all substances on the EU market (CEC, 2001, p6). 

Table4.1 Examples of toxicophoric substituents encountered in commercial substances, and the resulting toxicity often caused by chemicals that contain these toxicophores .

Table 4.2 Examples of electrophilic toxicophores commonly encountered in commercial substances, the reactions they undergo with biological nucleophiles, and the resulting toxicity3. ... 

Most industrially developed nations have government agencies that assess risk to human health and the environment resulting from the manufacture and use of chemical substances. Industry, consultants, academics, and the research community also undertake such assessments. For example, in the U.S., the Office of Prevention, Pesticides, and Toxic Substances (OPPTS) devotes considerable resources to risk analyses in its review of commercial substances that are or will be released to the environment. Canada has a similar system, and so do most nations in the European Union and Japan. As the number of potentially hazardous substances introduced into commerce grows, maximizing the efficiency of these assessments becomes increasingly important. 

There is general agreement that an artefact for the realisation of the unit mole as the top of the traceability chain is not needed/rational. However, there is a large variety of opinions on the nature of the link to the SI. They range from primary methods through pure elements to commercial substances. Often we hear objections that the uncertainty at this level is negligible compared to that in routine measurements, so that work at this level is unimportant. This is usually true for trace constituents, but for analysis of major or minor components standards may be a significant source of error. 

Pure substances are obviously needed for calibration of the measurement stage of a method. Very often, commercial substances are used as pure standards and the level of uncertainty associated with the purity contributes to the uncertainty of the measurement. Of course, a bias can be introduced in the measurement if... 

The commercial substance (pyrolusite) usually contains considerable quantities of chlorides. 

Although the breaks in o/lgCs curves are not very sharp (apparently the commercial substances are neither pure nor monodisperse), values of CMC, 1 -1 O 4 mol dm 3 for P85 and 3-10 mol dm 3 for F108, can be reliably determined. From the slope of the line drawn below... 

Note. The commercial substance known as wood naphtha , pyroxylic spirit or wood spirit contains 60 to 90% of methanol, together with acetone and other empyreumatic impurities. The variety used for denaturing ethanol (see under Ethanol) contains not less than 72% v/v of methanol. 

Distillation Products.— The importance of petroleuni as a commercial substance lies in the wide industrial use of the various products obtained from it by distillation. As petroleum is a mixture of gaseous liquid and solid hydrocarbons both it and its distillation products are... 

We come now to a series of compounds which has in it many well-known substances, and to which the class name of alcohols has been given. The two most common representatives of the series are ordinary alcohol or grain alcohol and wood alcohol. Both are valuable commerci substances, the former being obtained by the distillation of fermented grain or fruit, the latter by the distillation of wood, hence their names. The composition and empirical formulas of the two are similar, viz.. 

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