146 ANNUAL REPORT 
2.68 
we find that the available hydrogen is 4.13—~3— ==3.80 per cent. 
Now 83.75 parts by weight of carbon require 2 83.75=223.32 parts . 
of oxygen, while the hydrogen requires 3.8X8=30.40 parts of oxygen, 
the total parts by weight of oxygen for 100 parts of the coal being thus 
223.324 30.40=253.72. Since the air contains 21 per cent. by volume of 
oxygen there are used for the combustion of the carbon. 
| 21 X 223.32 
253-72 
The hydrogen requires 
21 X 30.4 
253-72 
But every volume of oxygen on combustion furnishes one volume 
of carbon dioxide; therefore on using the above coal the ratio of the car- 
bon dioxide to the nitrogen must be 18.49 :79. 
In the burning of cement, where a considerable amount of the fire 
gases is made up of carbon dioxide from the decomposition of the calcium 
carbonate, it may be desirable to know the amount of the CO, present 
in the gases resulting from the limestone. Knowing the total amount of 
carbon dioxide shown by the analysis we can calculate the amount of 
this gas due to the combustion alone from the percentage of air repre- 
sented by the analysis as calculated from the expression, I00N—N— 
3.760. 
If we let the per cent. of air be equal to a, and’ assuming that a 
coal is used of the composition given above, the carbon dioxide produced 
N.a 
in the combustion must be obtained by the expression 79 :18.49=—— :X or 
100 
=18.49 volumes of oxygen. 
=2.52 volumes of oxygen. 
If, for example, the nitrogen found by the analysis is 
100X790 
69 per cent., the air used=95 per cent. and the carbon dioxide=30 per 
cent. and the carbon dioxide evolved from the limestone must be 30—15.34 
==T4OO Der Cea. 
MECHANICAL ANALYSIS OF RAW MIXTURES AND CEMENTS. 
Sieve Analysis. —The fineness of grain of the mineral constituents 
of a clay governs to a large extent its chemical activity, and hence it 
becomes an important and interesting problem to bring about a separation 
of the various sizes of grain. The simplest and most obvious method 
of separation is the sieve analysis, in which the material to be examined 
is passed either in a dry or wet state through a series of sieves. The 
usual combination for a sieve analysis as practiced in the laboratory of 
