12 THE SPECIFIC HEAT OF WOOD. 



Dieterici, but checked the value by determining the specific heats of 

 lead and zinc. 



The factor 15.44 was used in the present work. This value was 

 checked at the end of the work by determining the heat of neutraliza- 

 tion of hydrochloric acid with sodium hydroxide. (See Appendix.) 



THE BALANCE. 



A Spoerhase analytical balance (see Plate I), sensitive to one- 

 fiftieth of a milligram, and a set of first-quality Sartorius weights, 

 were used in all determinations of weight, but fractions of a milli- 

 gram were disregarded in the regular series of weighings. 



In weighing the cups of mercury a counterpoise was used to avoid 

 wear of the larger weights. This counterpoise was a cup half filled 

 with mercury and covered with a plate of glass sealed on with Can- 

 ada balsam. Inasmuch as differences in the weight of the cups were 

 alone significant, the weight of this counterpoise was not determined. 



WEIGHT, TEMPERATURE, AND VOLUME DETERMINATIONS. 



The green or air-dry cylinders were first brought to the oven-dry 

 condition by being placed in the oven at about 105 centigrade for 

 about two days and then weighed at intervals until their weight 

 became constant to within 1 milligram for eight hours. This constant 

 weight was recorded 1 in each case as the oven-dry weight of the 

 specimen. The cylinder, before being weighed, was cooled in a 

 stoppered test tube and then transferred to a vessel of known weight 

 in which it was placed on the balance pan. 



The oven-dry cylinder was brought to an even temperature all 

 through by being held in the oven for at least 18 hours after the oven- 

 dry condition had been reached, during the last half hour of which 

 the temperature of the oven was kept constant to within one-tenth 

 of a degree centigrade. The bulb of the thermometer was within 

 a centimeter of the cylinder to be used in the ensuing run. 



The transfer from the oven to the calorimeter was made in a pair 

 of silvered Dewar tubes. The cylinder was placed in the smaller 

 tube, fitting it loosely, and the smaller tube inserted, mouth first, 

 into the larger one. These tubes were kept in the oven except when 

 in use and always had the same temperature as the wood they 

 carried. 



At the end of the experiments the densities of all cylinders were 

 found by measuring their volumes through the displacement of 

 mercury in a graduated cylinder. This method failed only with red 

 oak, into the vessels of which the mercury entered. 



