Adulteration process water

Ash.—The dry residue from the determination of the water is incinerated and the ash weighed. If this exceeds 1%, adulteration with mineral matter is probable, this being confirmed by qualitative analysis of the ash. Such analysis is useful in any case to detect the presence of heavy metals (especially iron), which may be introduced during the manufacturing processes and are harmful in the dyeing. The ash of alizarin consists normally of sodium or calcium salts. 

A good solvent should (i) not react with the drugs being analysed (in this case, for example, with the hydroxide groups of some opiates), (ii) be volatile, to allow rapid application of a small spot of solvent and at the same time concentrate the sample prior to analysis, (Hi) freely dissolve all of the drugs of interest, so that they are determined quantitatively and at the same time no solid material is present in the mixture immediately prior to analysis after removal of the insoluble adulterants, and (iv) be free of water, to prevent deactivation of the silica gel and to reduce the risk of sample hydrolysis during the process of sample application to the TLC plate. 

The suspected gum is coven with ten times its quantity of hot water, and allowed to stand for three or four hours, v/ith frequent stirring. When the instduble matter has subsided, half the liquid is poured off, replaced by the same quantity of cold water, and again well stirred. This process is repeated twice within an hour. The last mixture separates after short standing into two parts, the upper layer consisting of water, and the tower layer of a gelatinous, highly refractive mass. In this way, the presence of even 5 per cent, of adulterant can be detected with certainty. 

Water penetration rates are usually calculated according to the gas laws from measurement of pressure decay upstream of the filler over the whole period of testing with the gas (air) volume above the fluid held constant. They are therefore subject to temperature variations. Although the principle of the water penetration test is sound, and the avoidance of the use of potentially adulterating solvents is attractive, the low rates of water penetration calculable from only very small pressure drops within test systems have raised doubts about the robustness of the method for routine application in its contribution to the decision-making process. 

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