COMBUSTION AND FUELS 87 



boiler inspection and insurance companies, who would be most 

 likely to know, have made mention of no cases of excessive 

 pitting or corrosion directly traceable to the presence of sul- 

 phur in oil fuel. Some of the lower grades of bituminous- 

 coal, containing from 2 to 4% of sulphur, have been used in 

 steam-boiler furnaces without detriment to the boilers, although 

 the grate bars may have been affected. Consequently, there 

 seems to be no good reason why oil containing sulphur cannot 

 be burned with the same freedom from deteriorating effects 

 on the boiler. 



Flash Point and Firing Point. If a sample of fuel oil or of 

 crude oil is placed in an open cup and heat is applied, the oil 

 will begin to vaporize and inflammable gases will be driven 

 off. If, while the heating proceeds, a lighted match is passed 

 at intervals over the surface of the oil and about in. from it, a 

 point will be reached at which the vapor rising from the oil 

 will ignite and burn with a flicker of blue flame. The tempera- 

 ture of the oil when this flame first becomes apparent is 

 termed the flash point of the oil. If the heating of the sample 

 is continued, the vapors will be given off more rapidly and 

 eventually they will ignite and burn continuously at the sur- 

 face of the oil when the lighted match is brought near. The 

 temperature of the oil when the burning becomes continuous 

 is termed the firing point of the oil. The flash point and the 

 firing point of an oil depend on the composition, specific grav- 

 ity, and source of the oil. 



Specifications for Oil Fuel. An oil to be used as a fuel for 

 steam boilers may be either a crude oil of uniform composition 

 or a fuel oil. If it is the latter, all constituents having a low 

 flash point will have been removed by distillation. The dis- 

 tillation should not have been carried on at a temperature high 

 enough to burn the oil or to cause particles of carbon to sepa- 

 rate from the oil; for these carbon particles will eventually clog 

 the pipes and burners and cause trouble. The flash point of 

 an oil fuel, as determined by a standard testing apparatus, 

 should not be below 140 F.; otherwise, there will be danger 

 from the inflammable vapors given off. The percentage of 

 water in the oil should be less than 2, and the percentage of 

 sulphur should not exceed about 1. If these proportions are 



