RECORDS OF MEETINGS OF 1909 
321 
and the two to be separated by a layer of oil; then the layer of lubricant next 
to xx moves along with it, while that next to yy remains stationary. The 
intermediate layers of lubricant may be considered as moving one upon 
another, and the resistance offered to this motion is caused by the viscosity 
or internal friction of the lubricant considered. It is obvious then that the 
measurement of the viscosity of oils and the way in which this property is 
influenced by certain conditions should be an important consideration when 
it comes to a question of the suitableness of an oil for any particular purpose. 
It might be mentioned at this point, also, that although viscosity is an essen¬ 
tial characteristic of liquid lubricants, the presence of this property alone 
does not qualify a substance for lubricating purposes. Molasses for example 
is very viscous, but lacks the so-called “body” or “oiliness” which would 
enable it to insinuate itself between two surfaces and maintain there, a 
sufficient thickness of material to prevent actual contract of the moving 
parts. Various methods have been suggested for the measurement of the 
liquid friction or viscosity of a lubricant, the most practical of which consists 
in noting the time it takes for a given quantity to flow through a small opening 
at a constant temperature. In Germany the Engler, in England the Red¬ 
wood, and in the United States the Saybolt are the chief forms used. 
In practical work the determination of the gravity and the viscosity, as 
a rule, furnishes sufficient check upon the raw materials and the finished 
products. It is, however, very often necessary and important that other 
physical tests be applied. To prevent the use of oils which might, when 
heated, give off inflammable gases the determination of the “flash point” 
and “fire point” becomes essential. 
Some lubricants, too, are used at very low temperature, for instance, in 
the operation of an ammonia compressor, and here it is important that the 
lubricant should not solidify by the action of the cold, for under these con¬ 
ditions the energy needed to operate the machine would be very materially 
increased. 
We have then these six physical tests, (1) Gravity, (2) Flash, (3) Fire, 
(4) Chill, (5) Cold, (6) Viscosity, which are usually sufficient to O. K. or 
condemn a lubricant. 
If in dealing with lubricating materials, we only had to consider petro¬ 
leum products the above tests would be all that would be required. Many 
of the lubricants on the market to-day, however, contain varying small 
percentages of the so-called “fixed oils” which are either of plant or animal 
origin and whose detection and estimation, though important, involves 
purely chemical process and cannot be taken up at this time. 
The Section then adjourned. 
William Campbell, 
Secretary. 
