As a result of this sweating operation there is produced “crude scale wax,” the ordinary wax of commerce. It is yellow to ivory in colour, contains only a small proportion of oil and is almost odourless and tasteless. The crude scale wax is very commonly further refined by the general methods used throughout the oil industry, i.e. by treatment with acid and alkali, and by filtration, to produce refined paraffine wax of pure white colour, free from oil, and without odour or taste. It is this refined grade of wax which is commonly met with in the retail market. Returning to the wax-free oil which passes through the canvas filters, leaving behind the impure wax, we find that this is the product from which lubricating oils are obtained. It is an oil of dark brown or amber colour, considerably heavier than kerosene and has a very greasy feeling which is indicative of its value for lubricating purposes. Elaborate methods have been devised for accurately determining and gauging this greasiness or viscosity, which is the property of the oil upon which its lubricating value is most dependent. In general, this oil is in part re-distilled, that is, it is charged into a still and subjected to a temperature which is sufficient to drive off, in the form of vapour, some portion, though not all of the oil under treatment. This process, accurately described as “reducing” the oil, serves to concentrate in the residue remaining in the still, the heavier or more greasy or viscous constituents, the grade or viscosity of the lubricating oil depending on the extent to which this reduction is carried. As in the case of the other petroleum products, it is customary to carry out a chemical purification process and to filter the oil subsequent to the re-distillation. As a result of such further chemical purification and filtration, the colour of the oil is improved, any suspended solids or dirt which it may contain are removed, and any chemical constituents which it may contain and which may be detrimental to its use, are destroyed.