198 Pechham and Linton — Trinidad Pitch. 



and the weight of the mass upon itself have rendered the mass 

 within the hold of the ship nearly solid and the material is no 

 longer the natural crude pitch, but something more or less 

 removed from it by loss of water and gas. 



In the case of samples like those taken by ourselves and 

 packed in a trunk, labelled and carefully wrapped in paper, the 

 loss of water was nearly complete before they reached New 

 York. In fact it required only a week or ten days in Port of 

 Spain to completely transform the cheese pitch from a moist, 

 porous substance, cutting with a knife like cheese, to a hard 

 brittle solid, readily broken into fragments that could only be 

 cut with considerable difficulty, provided it was kept out of the 

 sun. It is therefore manifest that commercial samples of crude 

 pitch are not samples of natural crude pitch ; nor is it possible 

 to bring away from Trinidad samples of " cheese " pitch in the 

 natural condition. We therefore determined to analyze the 

 specimens selected free from water and gas, and thus render 

 the results comparable. 



The samples were severally coarsely powdered and air dried 

 by placing them upon the laboratory table in the sun. In dry 

 weather they soon dried to a constant weight. In damp 

 weather they lost and gained within narrow limits indefinitely. 

 Heated in an air bath to 50° C, they were soon brought to a con- 

 stant weight. Heated at 100° C, to a constant weight, a vary- 

 ing loss of volatile oils invariably followed, which showed that 

 determinations of water at 100° C. as a constituent of the pitch 

 leads to vitiated results from two sources : first, the percentage 

 of water is not constant in the same specimen but varies with 

 the condition of the atmosphere ; second, pitch that is appar- 

 ently very dry gives off an appreciable amount of volatile 

 oils below 100° C. The samples were therefore dried to a 

 constant weight, at a temperature below 50° C. Of course, 

 if, for any reason, the amount of water in a given specimen 

 of pitch is desired, it is easily ascertained, but it should not be 

 reported as a constituent of the pitch, as the varying per- 

 centage of water causes all of the other percentages to vary 

 in the same specimen at different times. 



The dried specimens were then exhausted with petroleum 

 ether. In the present instance the petroleum ether used for 

 all the specimens came from the same barrel and was of specific 

 gravity 74° B. The exhausted residues were dried at 100° 

 O. and the difference in weight was computed as petrolene. 

 The dried residues were then exhausted with boiling spirits of 

 turpentine, washed with ethyl alcohol and dried at 100° C. to 

 a constant weight. The loss was noted. The dried residues 

 were then exhausted with chloroform and dried and the loss 

 noted. The loss by turpentine plus the loss by chloroform is 



