The Saybolt viscosity of blends. . tors which are intermediate between the extreme values forblends of unlike crudes. VIII. GRAPHICAL REPRESENTATION OF RESULTS OF TESTS Fig. 4 shows the results of tests except those of Table No. 5,Series 2, which were omitted to avoid confusion. It will benoted that the time ratio, or correction factor, is not a minimumfor the 50 per cent blends, as might be expected. The points forthese blends are located on vertical dotted lines, there being oneblend in Espys tests and in Series 1, and four blends in Series 3and 4. i8 Technologic Papers of the Bureau of Stan
The Saybolt viscosity of blends. . tors which are intermediate between the extreme values forblends of unlike crudes. VIII. GRAPHICAL REPRESENTATION OF RESULTS OF TESTS Fig. 4 shows the results of tests except those of Table No. 5,Series 2, which were omitted to avoid confusion. It will benoted that the time ratio, or correction factor, is not a minimumfor the 50 per cent blends, as might be expected. The points forthese blends are located on vertical dotted lines, there being oneblend in Espys tests and in Series 1, and four blends in Series 3and 4. i8 Technologic Papers of the Bureau of Standards Assuming that the points should lie on smooth curves, Fig. 4may be used as an indication of the reliability of the tests. Bspystests and those of Series 1, for example, show greater irregulari-ties in Fig. 4 than when plotted in the form of Fig. 1. While thefigure is convenient for interpolation between tests in a series ofblends of two given components, it is not convenient for inter-polation between one series and FlG. 4.—The relation between viscosity as determined by test, and as estimated by thelogarithmic rule By the use of Fig. 3 the viscosity of a blend could be obtainedon the assumption that it depended upon only three independentvariables, the Saybolt viscosities of the two component oils and theirproportions. But experiment has shown that the viscosity of ablend also depends upon the source of the crude, and it is possiblethat the range of boiling point should also be taken into account. In order to reduce the number of variables and facilitate graph-ical representation it was decided to concentrate attention upon50 per cent blends. If the correction factor for this blend is knownthe factors for other proportions may be estimated by sketching incurves similar in shape to those of Fig. 4. The variable due tosource may be eliminated by using separate diagrams for naph-thene and paraffin crudes, as the difference between them is not sogreat as to make
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