566 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



leiim of a mean specified gravity of about 43° Baiime. "When 

 the crude petroleum is too heavy, the gaseous and very volatile 

 products may be entirely absent, even to such a degree as to cause 

 a loss for the opposite reason, leaving too large a quantity of tar, 

 the result of an excess of non-volatile matter. Such oils are there- 

 fore used as lubricators. Besides this variety in crude petroleum, 

 the petroleums of different wells (of which the fundamental for- 

 mula is, as I will below explain, Cn Hn -j- i, H) differ as much in 

 the incidental substances the}' contain in solution or suspension as 

 the wat< r (of which the fundamental formula is Ho) of different 

 springs. 



In the same manner as waters differ in containing salts of lime, 

 soda, potassa, etc., or chlorides, bromides, iodides, sulphates, etc., 

 so crude petroleums differ in containing oxygen or sulphur, nitro- 

 gen or phosphorus, arsenic, iron. etc. These incidental constitu- 

 ents, some of which are left behind, in the remnant of the distilla- 

 tion (the tar), have nothing to do with the chemical composition 

 of the pure petroleum, the same as pure distilled water is indepen- 

 dent of the incidental salts it contained before the distillation. 

 Analyzing the tar or coke left from different kinds of petroleum 

 demonstrates the presence of quite a variety of ingredients, which, 

 however, will teach us as little about the nature of pure petroleum, 

 as the analysis of the salts of mineral waters will teach us about 

 the nature of the chemical composition of water; and even as 

 eudiometric experiments are the most striking proof that pure 

 water is H O, so eudiometric experiments prove that pure petro- 

 leum is C H, though with certain variable cocfEcicnts, which I will 

 explain. 



I intend later to publish a separate paper containing all the 

 details of my quantative analysis, which would take up too much 

 time, and besides be dry and uninteresting to most hearers. I 

 will in the first place only state, that (as might be anticipated) the 

 amount of hydrogen is largest in the first gaseous products of the 

 distillation, less in the lighter fluids, as gasoline, naptha, benzine, 

 still less in kerosene, and least of all in paraffine. These substances 

 are all constant in their atomic constitution, although they are apt 

 to contain variable quantities of the volatile constituents of crude 

 petroleum (as oxygen, sulphuretted, phosphoretted or arseni- 

 uretted hydrogen, etc.), always comparatively very small, but 

 enou<T^h to give the distillates their strong characteristic odor. 

 They are easily removed by concentrated sulphuric acid, which 



