THE OIL- WATER TREATMENT. 77 
THE CRUDE-PETROLEUM TREATMENT. 
Crude petroleum is used in exactly the same way as is the common 
illuminating oil referred to above. Its advantage over kerosene is 
hat. as it contains a very large percentage of the heavy oils, it does 
lot penetrate the bark so readily, and. on the other hand, only the 
light oils evaporate, leaving a coating of the heavy oils on the bark, 
which remains in evidence for months and prevents any young scale 
which may come from the chance individuals that were not reached 
by the spray from getting a foothold. Crude petroleum comes in a 
great many different forms, depending upon the locality, the grade 
successfully experimented with in the work of this Bureau showing 
43° Baume. Crude oil showing a lower Baume than -±3 z is unsafe, 
and more than 45° is unnecessarily high. The lower specific gravity 
indicated (13 : ) is substantially that of the refined product, the removal 
of the lighter oils in refining practically offsetting the removal of the 
paraffin and vaseline. The same cautions and warnings apply to the 
crude as to the refined oil. 
THE OIL -WATER TREATMENT. 
Various pump manufacturers have now placed on the market spray- 
ing machines which mechanically mix kerosene or crude petroleum 
with water in the act of spraying. The attempt is to regulate the 
proportion of kerosene so that any desired percentage of oil can be 
thrown out with the water and be broken up by the nozzle into a sort 
of emulsion. Some of these machines, when everything is in good 
working order, give fairly satisfactory results, but absolute relia- 
bility is far from assured. 
The best outlook for good apparatus of this sort seems to be in car- 
rying the oil and water in separate lines of hose to the nozzle, uniting 
them in the latter, and in maintaining an absolute equality of pressure 
on both the oil and the water tanks by employing compressed air as 
the motive force, kept up by an air pump, the air chamber communi- 
cating with both of the liquid receptacles. Any other source of con- 
stant pressure, as carbonic acid gas or steam, will answer. One or 
more manufacturers are now working on apparatus of this general 
description. A 10-per-cent strength kerosene can be used for a sum- 
mer spray on trees where the San Jose scale is multiplying rapidly and 
where it is not desirable to let it go unchecked until the time for the 
winter treatment. The winter treatment with the water-kerosene 
sprays may be made at a strength of 20 per cent of the oil. Appli- 
cations of the oil-water spray should be attended with the same pre- 
cautions as with the pure oil, and there is even somewhat greater risk, 
owing to the natural tendency one has to apply the dilute mixture 
much more freely than the pure oil. The application should be merely 
