PHILLIPS. — COMPOSITION OF NATURAL GAS. 75 



by means of a slow stream of carbon dioxide generated by tbe action 

 of concentrated hydrochloric acid upon calcite in the large jar M. This 

 jar contained about five pounds of calcite at starting. The escaping 

 carbon dioxide passed through fragments of calcite in the tube K, and 

 through water in the bottle G. From this wash-bottle the iias stream 

 could be deflected to the right hand end of the combustion tube, as seen 

 in the sketch, entering this tube by the stopcock Z in rinsing gas into 

 the absorption vessel Q, or to the left, by way of the stopcock ZZ in 

 rinsing gas back into the vessel A. In this manner the rinsing out of 

 the products of combustion into either A or Q could be made very com- 

 plete. The tube F, descending into water in the open cylinder FF, 

 served as a safety valve to permit the escape of surplus carbon dioxide 

 from the generator, and thus any unsafe pressure in the apparatus was 

 avoided. The carbon dioxide could, therefore, be generated freely and 

 utilized only in so far as it was needed. It is to be observed that the 

 long glass tube connecting the stopcocks Z and ZZ lies in the, same 

 horizontal plane with the combustion tube HH, although in the sketch 

 it appears lower, in order that the arrangement of parts may be rendered 

 clear. The carbon dioxide having been absorbed in Q, the residual gas 

 was ready for measurement which was accomplished in the eudiometer 

 P over mercury. This eudiometer was of 100 c. c. capacity, being made 

 very short as shown (about forty centimeters long). It was graduated 

 only in its uppermost and lowermost portions. This is a convenient form 

 of eudiometer where mercury is used, as it avoids the great pressure of 

 a high mercury column, and consequent danger of leakage through the 

 stopcocks, so common where a high column of mercury is used. It is 

 easily seen that by lowering sufficiently the bottle R any volume of gas, 

 up to 100 c. c. may be readily measured. The combustion furnace stood 

 somewhat higher than the upper end of the eudiometer. It was sur- 

 rounded closely by sheet iron sides, which served to carry upward the- 

 waste heat. No difficulty was experienced in maintaining a constant 

 temperature about the eudiometer, as indicated by a thermometer read- 

 ing to 0.05°, placed in contact with its sides. By reason of the strong 

 upward draught produced by a sheet iron box placed around and in close 

 contact with the sides and ends of an ordinary combustion furnace, much 

 may be done towards diminishing the discomfort of the experimenter, 

 while the temperature of the interior of the furnace is increased, and 

 the ends of the tube are more readily kept cool. The tube tt, dipping 

 into water in the beaker T, serves to discharge the absorption vessel 

 after a determination. In a similar manner the eudiometer may be 



