We have already said that it does not suffice to admit the exact quantity of air necessary for the conversion of the sulphur into sulphuric acid, but that to get good working results there should be an excess of oxygen amounting to 5 per cent. beyond that theoretically needed. We have also already seen that every 14 parts of sulphurous n, d containing 14 volumes of oxygen, and needing a further 7 volumes of oxygen for conversion into sulphuric acid, besides the 5.18 volutnes of oxygen in excess+, will need, 14 + 7 + 5.18 + = 21 5.18 = 26.18 volumes 0 79 + 19.50 = 98'50 N Or together 100 + 24.68 = 124.68 volumes of atmospheric air carried 124* W7 into the chambir system. Hence for each volume of sulphurous acid 8.906 volumes of 14 air are necessary.
Now 1 litre of sulphurous acid at a temperature of Op C., and a pressure of 760 mine., weighs, ns we have seen, 2'8731 grammes, and the sulphurous acid stands as, 1 equiv. sulphur .. = 16 2 oxygen .. = 16 1 equiv. sulphurous acid = 32, therefore 1 litre of sulphumus acid at 0' C., and 760 mme.
2.8731 = 1.43655 grammes sulphur2 and 1.4:1655 oxyge n Total 2 67:310 grammes.
There are consequently for each 1'43655 grammes of sulphur used 8.906 litres of air toquired at 0° and 760 nime. Hence we find from the proportion, 1.43655 : 1000 = 8.906 : that for 89oli each 1000 grammes, or 1 kilogramme of sulphur, = 6199 litres or 6.199 cubic metres of air at 0° C. and 760 mine. pressure, must be introduced into the sulphur-burner, which = 6199 ; 1.2932 = 8017 grammes, or 8.0 t7 kilos.
In order to calculate the volume of air introduced at other temperatures and pressures upon the bases giveu above, we must remembar that 1 volume of the gas at 0° C. gives at t° C. (the pressure (27:3 + t) V remaining the same) 273 + t volume, and makes at V volume volume.
273 273Further, it is known that the volumes of such gases stand in iuverse proportion to the pressure ; (273 + t) V(27:1 + r V: 769accordingly the pressure of b mme. on the volume gives the volume 273 273, b (273 + t)V (273 + ti V; 760 according to the proportion b : 760 - : x, whence it follows that x = 273 273; b With the aid of the above formula it is easy to reckon the volume assumed by any volumo of air at 0^ C. and 760 mme., under any variation of temperature and pressine. It shows, for example, that the 6199 litres of flil' at 0°C. and 760 rnme. necessary for 1 kilo. of sulphur, have n volume at
(273 + 20) 6199 ; 760 293 ; 6199 20° C. of = = 6654 litres.
27'3 ; 760 273 The above proportions refer, however, to dry air, whilst the atmosphere is never free final moisture, which has a distinct influence upon the volume. In order to arrive at the eorrect figure, e must also take this moisture into consideration.
When a gas under b pressure is saturated with water, its tension is lessened lty that of the noisture, or b c, when the tension of the moisture is c, so that now the mixture of gas and noisture has the same tensiou whieh the gas alone had formerly. As the moisture reduces the gas he Inttur changes its volume in the inverse proportion of the tension. Then, from the volume 273 + tYV ; 76°, when V is the original volume of the dry gas at 0° C. and 760 mme., we derive the 273 ; b icw volume V' = (273 + t)V; 760 through the saturation with moisture. 273 (b e) Then from the formula wherein the increase of temperature and moisture makes the tension (273 + 20) 6199 ; 760 293 ; 6199 ; 760 .
7'391 mme., we get , = 6809 litres.
273 (760 17.391) 2 ; 142 609Tho foregoing calculations show then that for each kilogramme of chan sulphur burnt for the tanufacture of sulphuric acid, the admission of the following air is necessary : 6199 litres dry air at 0' C. and 760 mme., or t11W + 154 = 6653 20° C. or 6653 + 156 = 6t-09 air saturated a ith moisture at 20° C. and 760 mum. pressule.
The lest 156 litres increase allowed for the moisture of the air is greater than is really ordinarily necessary, as the atmosphere is often net saturated with moisture. But as this increase is only 2.34 per cent. of the volume of dry air, whilst about 24.68 per cent. (or mere than ten times as much) of excess air is introduced beyond the theoretical requirementS, the changes in the moisture of the air and the differences in its volume resulting therefrom, have little effect upon the practical working. No further discussion therefore is necessary concerning them.
From the foregoing observations it is self-evident that the volume of air required on the average for a certain consumption of sulphur will depend also upon the altitude of the works; which affects the B pressure. Fur example, the quantity of air will occupy 51 per cent. greater space at Munich than at Marseilles.