204 Transactions of the American Institute. 



it bursts into flame, and produces phosphoric acid. It has a slow 

 combustion, and a high combustion; requiring for the former a 

 temperature of 77°, and for the latter of 140 Q , Fahr. 



Charcoal burns slowly at a dull, red heat. Sulphur takes fire at a 

 temperature of about 550°. Most of the elementary bodies require 

 a temperature of redness to cause them to take fire. When I intro- 

 duced the sodium into this jar of chlorine, it was necessary to heat 

 it to the temperature at which it would begin to combine. 



Hydrogen has a curious relation to chlorine. If we mix them in 

 the dark, they remain without combining ; but if we allow the sun- 

 light to fall upon them, they combine ; so that the burning point in 

 that case depends on the presence or absence of light. 



If we mix phosphorus and iodine at ordinary temperatures, they 

 combine, producing light and heat ; but if we make the experiment 

 in an atmosphere cooled by ice, they fail to combine. The burning 

 point is about the ordinary temperature of the atmosphere. 



The burning point is a matter of great importance, with regard, 

 particularly, to the petroleum which has been so extensively intro- 

 duced of late. I have before me two products of petroleum. This, is 

 a sample of a good quality of kerosene; and this, is a sample of what 

 some unscrupulous persons sell in New York as " safety gas ; " the 

 burning point of which is so low, that, although I have made the 

 experiment in the coldest days in winter, I have never found it cold 

 enough to fail to take fire from a lighted match. I suppose the point 

 at which it would refuse to burn, if there be one, must be 40° or 50° 

 below zero. I shall experiment with these oils by and by. I will 

 now merely explain the mode of testing them. 



The operation of testing kerosene is very simple. It is merely 

 ascertaining the temperature at which the oil evolves an inflammable 

 vapor, the " flashing point," and the temperature at which the oil 

 takes fire, " the burning point." But when I say the operation is 

 very simple, I do not mean to say that any person is qualified to make 

 the test in a reliable manner until he has been properly instructed. 

 In careless, ignorant hands results may deviate twenty or thirty 

 degrees from the truth ; while in skillful hands four or five degrees 

 will cover the most divergent results. 



A suitable apparatus is required ; consisting of a cup to hold the 

 oil, surrounded by a vessel of water, which is heated by a small spirit 

 lamp ; the bulb of a thermometer is immersed in the oil. The tester 

 legalized in the schedule of the English Petroleum Act is a very 

 good one. The open tester of Tagliabue is a very good instrument, 



