THE OIL-WATEK 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 

 that, as it contains a very large percentage of the heavy oils, it does 

 not 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 43° is unsafe, 

 and more than 45° is unnecessarily high. The lower specific gravity 

 indicated (43°) 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 b}^ 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 spra}^ 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 spra}^ 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 dihite mixture 

 much more freely than the pure oil. The application should be merely 



