The analysis and grading of creosotes . d 320° there shall be no oily residue in-soluble in caustic alkalies. The water shall not exceed 1 per shall be no admixture of undistilled tar. Grade B.—The percentage weights on distillation by the labora-tory method shall fall within the shaded limits in figure 24. The [Cir. 112] i 43 specifications for index of refraction, specific gravity, and sulphona-tion test are the same as for Grade A. The water shall not exceed 2per cent. There shall be no admixture of undistilled tar. Grade C.—The percentage weights on distillation, according tothe
The analysis and grading of creosotes . d 320° there shall be no oily residue in-soluble in caustic alkalies. The water shall not exceed 1 per shall be no admixture of undistilled tar. Grade B.—The percentage weights on distillation by the labora-tory method shall fall within the shaded limits in figure 24. The [Cir. 112] i 43 specifications for index of refraction, specific gravity, and sulphona-tion test are the same as for Grade A. The water shall not exceed 2per cent. There shall be no admixture of undistilled tar. Grade C.—The percentage weights on distillation, according tothe laboratory method, shall fall within the limits shown in figure25, and the indices of refraction shall fall w^ithin the limits shown infigure 26. The volume of the sulphonation residue in the fraction,305°-320°, shall not be greater than one-tenth of the weight of thefraction. The Avater shall not exceed 4 per cent. There shall be noadmixture of undistilled tar. Grade D.—The distillation limits are shown in figure 27, and the. ^ 220 230 24-0 250 260 270 280 290 300 3^0 TEMPEiRATURE Fig. 28.—Index of refraction limits for Grade D. indices of refraction shall fall within the limits shown in figure volume of the sulphonation residue from the fraction, 305° to320°, shall not exceed one-fifth of the weight of that fraction. Thewater in the creosote shall not exceed 5 per cent, and admixture ofundistilled tar or other viscous material shall not exceed 15 per cent. USES OF THE VARIOUS GRADES. The Grade A oil is adapted for open-tank treatments or otheroperations where excessive loss from volatilization is possible duringthe process. It should be a pure coal-tar creosote, consisting almostentirely of aromatic compounds. An oil of this sort is also particu-larly well adapted for use in processes where only a minimum quan-tity of the creosote is employed, such as an empty cell process, where [Cir. 112] 44 it is essential that nearly all of the oil used shall stay in
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