The use of crude (unrefined) mineral oil in steam boilers is attended
by risks caused by impurities and foreign substances mixed with it.
These are likely to combine with the earthy matter in the water and
tend to form instead of preventing scale; the tar and wax contained in
crude petroleum combine with the sediment in steam boilers, and the
paste prevents the water from reaching and protecting the plates. This
is true particularly in shell boilers which have flat surfaces over the
fire. Refined mineral oil has none of these disadvantages.
Kerosene oil has all the advantages to be derived from the use of crude
petroleum and the above objections quite removed.
In one system of the application of steam the use of kerosene and
petroleum cannot be recommended: that is _when live steam is used for
cooking purposes_, the odor from the oil will impregnate the meat and
other products designed for food consumption.