Simple Oil Tests for the Workshop.
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The sender of ate following communication has been awarded the Ws. prize this week.
[1175] " W.A.E.V." (Stamford Hill) writes :--" It is rather important that drivers of steam and petrol wagons and also garage foremen should know a few simple tests for oils and greases. Many a valuable chassis has been spoiled by the use of unsuitable lubricants, and too many responsible men are, quite content to use any oil which happens to be at hand at the moment.
" The first simple test is for ascertaining the presence of acid. A polished copper plate should be immersed in the lubricant for a few moments. If there is no acid present, no change will be noticeable on the surface of the plate. A trace of acid, however, will dim the surface.
" To determine whether a mineral oil is pure, a small quantity of HsSO4 (sulphuric acid) should be added to a small quantity of the oil. Discoloration will follow if the oil contains any fatty material. The temperature should rise to about 35 degrees F.on the addition of the acid if the oil be of good quality.
" A test for the solidification of lubricating oil is to smear two polished iron plates with a thin layer of the oil. These should' then be placed one on the other with the treated surfaces in contact. After a few days, if the plates do not slide as freely as when the oil was first. applied, it may be taken that the oil is one that tends to solidify. " Should it be desired to test mixed oils containing both mineral and fatty constituents, a small quantity of the lubricant should be mixed with a strong solution of caustic potash. The whole should then be
shaken, and a fairly solid body will be formed varying in thickness or density with the quantity 4ìf fatty
matter present in the oil. Of course, this does not give any indication of the relative proportions of the mineral and fatty matters present. With a pure mineral oil there will be, at most, a slight cloudiness, but saponification will be marked if either animal or vegetable fats are present."