In general crude oil consists of carbon and hydrogen, though it also contains varying quantities of moisture, sulphur, nitrogen, arsenic, phosphorus and silt. The moisture contained may vary from less than 1 to over 30 per cent, depending upon the care taken to separate the water from the oil in pumping from the well. As in any fuel, this moisture affects the available heat of the oil, and in contracting for the purchase of fuel of this nature it is well to limit the per cent of moisture it may contain. A large portion of any contained moisture can be separated by settling and for this reason sufficient storage capacity should be supplied to provide time for such action. A method of obtaining approximately the percentage of moisture in crude oil which may be used successfully, particularly with lighter oils, is as follows. A burette graduated into 200 divisions is filled to the 100 mark with gasolene, and the remaining 100 divisions with the oil, which should be slightly warmed before mixing. The two are then shaken together and any shrinkage below the 200 mark filled up with oil. The mixture should then be allowed to stand in a warm place for 24 hours, during which the water and silt will settle to the bottom. Their percentage by volume can then be correctly read on the burette divisions, and the percentage by weight calculated from the specific gravities. This method is exceedingly approximate and where accurate results are required it should not be used. For such work, the distillation method should be used as follows: Gradually heat 100 cubic centimeters of the oil in a distillation flask to a temperature of 150 degrees centigrade; collect the distillate in a graduated tube and measure the resulting water. Such a method insures complete removal of water and reduces the error arising from the slight solubility of the water in gasolene. Two samples checked by the two methods for the amount of moisture present gave, _Distillation_ _Dilution_ _Per Cent_ _Per Cent_ 8.71 6.25 8.82 6.26 TABLE 46 COMPOSITION AND CALORIFIC VALUE OF VARIOUS OILS