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has also passed over, the net weight of the oil distilled over is ascer- 

 tained. With every change of receiver the temperature is noted, in 

 addition to which, apart from the odour and the colour, the weight 

 as well as its percentage proportion to the total weight of the sample 

 are determined and also its density and index of refraction. These 

 four values, percentage proportion, boiling point, specific gravity and 

 index of refraction, are placed in relation together by Geer and by 

 the system of Cartesian co-ordinates he enters the figures representing 

 the percentages by weight of the single fractions, as ordinates, the 

 abscissae are prepared once from the values for the boiling point, and 

 next for the density and refraction. This graphic arrangement of the 

 constants determined of each separate oil-fraction, gives a far better 

 survey of the greater or smaller degree of uniformity of a sample 

 than does the usual setting out of the values in tabular form, and 

 makes it possible to compare at a glance the corresponding properties 

 of different oils. 



In this manner Geer has examined an oil of turpentine from 

 gum, a crude "turpentine oil" obtained by steam distillation from 

 wood, a refined oil of same origin, and lastly a crude oil obtained 

 by dry distillation from pine wood. 



It goes without saying that in all the oil samples before distillation 

 the density and the refraction at 15 are ascertained, while colour, 

 odour, etc., are also observed. Genuine oil of turpentine, under the 

 co-ordinate system of percentage-figure and density, gave an almost 

 perpendicular line, corresponding to the fact that up to 92°/ distillate 

 the density remained almost entirely constant; similarly the curve which 

 was plotted from the relation between percentage and boiling point 

 showed up to about 9O°/ of the height a course almost parallel to the 

 axis of the ordinate. The curve which was plotted from the refraction 

 showed, corresponding to the steady slight increase of the index, a 

 direction gently inclining towards the axis of the ordinate, but this also 

 shows at about 85% a tendency to run parallel with the axis of the 

 abscissa. The third oil sample consisting of purified oil obtained from 

 wood by steam distillation also gave for the density a line running 

 parallel to the axis of the ordinate, which only changed into a curve 

 at 92°/ . But for boiling temperature and refraction the lines which 

 had run almost perpendicular up to 75% height, changed into curves 

 at that figure. From the almost equal course of the corresponding 

 curves of the two oils, Geer pronounced the purified oil of turpentine 

 from wood to be a very pure product of a quality equal to that of 

 oil of turpentine from gum. The curves which were plotted from 

 the constants of the fractions in the other two oils did not show 

 the same regular course as those mentioned above; the curves of the 

 oil prepared by dry distillation especially showed an entirely irregular 



