CALCULATION OP RESULTS. 65 



AMOUNT OF CARBON DIOXIDE ABSORBED. 



The weight of carbon dioxide absorbed was determined by noting the 

 increase in weight of each of the three soda-lime cylinders S, L,, and I and 

 the water-absorber No. 6, through which the air passed after leaving the 

 soda-lime cylinders. Soda-lime cylinder S weighed at the start 2,416.2 

 grams more than the counterpoise. At the end of two hours it was ob- 

 served that the weight had increased by 6. 5 grams. Similarly , cylinder L, 

 had increased in weight 18.8 grams and cylinder 1 2.5 grams, while water- 

 absorber No. 6 had increased in weight 16.3 grams. To find the total 

 weight of carbon dioxide during this period, therefore, the increases in 

 weight of these four parts of the carbon-dioxide absorbing system were 

 added together, the amount of carbon dioxide absorbed in the two re- 

 sidual analyses, i. e. , 0.09 gram, added, and the usual correction of 0.20 

 gram for the increase in weight of absorber No. 6 subtracted. It is 

 thus seen that the total weight of carbon dioxide absorbed during this 

 period was 43.99 grams. It will be noted on the blank that space is left 

 for a fourth soda-lime cylinder. Frequently, in experiments in which 

 there is an excessive amount of carbon dioxide absorbed, it becomes 

 necessary to stop the air current for a moment or two and replace an 

 exhausted soda-lime cylinder with a fresh one. 



AMOUNT OF OXYGEN ADMITTED. 



The calculation of the weight of oxygen admitted to the chamber is 

 carried out on the upper right-hand side of the blank. To avoid errors 

 and to aid in referring to the cylinder, the cylinder number is first re- 

 corded. The weight of the cylinder over and above the counterpoise at 

 the beginning of the period and the weight under the same conditions 

 at the end are recorded immediately beneath this. The difference, 

 which represents the loss in weight of the cylinder, is the weight of the 

 oxygen plus the nitrogen, for, owing to the purifying attachments on 

 the cylinder itself, the gas issuing from the rubber tube consists only of 

 oxygen and nitrogen. It becomes necessary, therefore, to calculate the 

 amount of nitrogen admitted with this oxygen, and this is done by 

 adding the logarithm of the percentage of nitrogen of this particular 

 cylinder, as determined by the analysis (see p. 34), to the logarithm of 

 the weight of oxygen and nitrogen admitted. The sum of these loga- 

 rithms is the logarithm of the weight of nitrogen, which, in this in- 

 stance, amounted to 0.67 gram, and, since the weight of the oxygen 

 plus the nitrogen was 46.78 grams, the true weight of oxygen admitted 

 during this period was 46. 1 1 grams. 



For purposes of calculation, to be explained beyond (p. 88), it is 

 desirable to know the volume of nitrogen admitted to the chamber, 



