FcKL Oils for Pimt luRir.ATiox 409 



viscous or if ,i;rcat accuracy is rccjuired, the water content .should be 

 determined by distillation. Kor this jmrpose 100 c. c. of the oil is 

 mixed with 100 c. c. of solvent, and the distillation is carried to a point 

 where the water in the receiving cup cannot be further increased. 

 Salt\- water is very corrosive in diesel engines. 



THERMAL VALUE 



The thermal or calorific value measures the theoretic power in 

 fuel, it is stated in British Thermal (heat) Units (B.T.U.) per 

 pound of fuel. Each B.T.U. is equivalent to 778 foot-pounds of work. 

 T!ie thermal value is determined in bomb calorimeters. 



Coal varies so widely in quality that determinations of the calori- 

 fic value become almost a necessity. Petroleum oils, however, vary 

 but slightly. California fuel oils have about 19,000 B.T.U. per pound. 

 Although the calorific value per pound decreases with the density, this 

 is overbalanced by the fact that oils are bought by volume and the 

 weight of a unit of volume increases faster than the calorific value de- 

 creases. A gallon of gas oil has about 8 percent more potential power 

 than a gallon of gasoline. 



OTHER TESTS 



Additional tests that are applied to gasoline are color, odor, and 

 acidity. A test for acidity is to shake the residue after distillation 

 with distilled water and to add a little methyl orange. For heavy oils 

 tests are made for coke residue, free carbon, acid and alkaline content, 

 resin, paraffin, and asphaltum. For lubricating oils the viscosity is of 

 great importance, and is best made in an Engler viscosimeter. 



California oils and most of the Texas and Oklahoma oils are of 

 the so-called asphalt base type. I'ennsylvania oils and much of the oil 

 from the mid-continent field are of the paraffin base type. 



TESTS OF FUEL OILS AT THE AGRICULTURAL EXPERI- 

 MENT STATION 



During the early years of the use of gas oil very few tests were 

 made, because the shipments were satisfactory to the users. Even the 

 low gravity gas oils contained sufficient gasoline to give low flash 

 points. Records of most of the early tests were not preserved. Since 

 1917 tests have been made on many oils, often at the request of the 

 local dealers or the users. Specific gravity and flash and burning- 

 point tests are listed in the accompanying table. 



