CARPENTER'S CALORIMETER. 33 



holding the fuel. At its top is a silver mirror, 38, to deflect 

 the heat. The plug is made of alternate layers of asbestos 

 and vulcanite. The products of combustion pass off through 

 the spiral tube, 28, 29, 30, 31, which is connected with the 

 small chamber, 39, attached to the outer case of the instru- 

 ment. This chamber has a pressure-gauge, 40, and a small 

 pinhole outlet, 41. Outside the chamber is the calorimetric 

 bath, i, which is connected with an open glass gauge, 9, 10. 

 Above the water is a diaphragm, 12, used to adjust the level. 



The calorimeter h'as an outer nickel-plated case, polished 

 on the inside. The bath holds about 5 pounds of water, and 

 uses about 2 grams of coal at a time. It is thus considerably 

 larger than the bomb, and the charge being larger the time 

 consumed by the test is longer, being some ten minutes for 

 each gram burnt. The entire outside dimensions of the case 

 are 9^ inches high and 6 inches diameter. 



In using the apparatus the coal is ground to a powder in a 

 mill or mortar. The asbestos cup is heated to burn off all 

 organic matter and weighed. The sample is then placed in 

 it, and the whole weighed again. This gives the weight of 

 the coal used. Place it in the combustion-chamber, raise the 

 platinum igniting wire above the coal, make the connections 

 with the battery, and as soon as the heat generated causes the 

 water to rise in the glass tube turn on the oxygen, and by 

 pulling down the wires kindle the coal. At this instant the 

 reading on the glass scale must be taken. 



By means of the glasses 33, 34, and 36 watch the 

 progress of the combustion, and as soon as finished take the 

 scale-reading and the time. The difference between this 

 scale-reading and the one previously made is the " actual " 

 scale-reading. 



To correct for radiation, allow the apparatus to stand with 

 the oxygen shut off for a length of time equal to that of the 

 combustion, and take the scale-reading and the time. The 



