150 REPORT—1845. 
the sulphurous acid, the anhydrous sulphuric acid robs the gypsum of part 
of its water, thus becoming hydrated sulphuric acid and losing its tension. 
When the oxygen is estimated, not by combustion with hydrogen, but by 
absorption with phosphorus, the precaution must always be taken to sepa- 
rate the vapours of phosphorous acid by a bullet of caustic potash, before 
effecting the measurement. 
As the tension of the aqueous vapour, and in fact every known precau- 
tionary means were adopted in our experiments, we believe it to be unne- 
cessary to enter into further detail. But, at the same time, as it is necessary 
that we should submit to the Association some proofs of the degree of accu- 
racy which we profess to have attained in this mode of analysis, we do not 
consider it superfluous to lay before it a series of analyses of common air, 
made with eudiometers such as have been described, but of various sizes, 
and with air collected at different times, the analyses being made with the 
precautions recommended by us. And we are less afraid of being accused 
of unnecessary detail, because these analyses show most decidedly that the 
presence of nitrogen during the combustion of hydrogen and oxygen does 
not cause the formation of ammonia, or of any degree of oxidation of ni- 
trogen. We thought this question, involving as it does the whole value of our 
labours, so important as to be submitted to rigorous experimental research. 
The air employed in these experiments was collected in the neighbour- 
hood of Marburg in the open air, and carefully freed from carbonic acid : 
the measurement of the respective volumes of gases was effected at the maxi- 
mum of moisture. 
I. Experiments with a eudiometer of small dimensions. 
Ist Experiment, June 14, 1844. 
Volume. i nee , aan of Barometer. 
iS m m 
Volume of air used creccsscccessesseeseese| 200°L 18:0 0:2075 0:7480 
Volume after admission of hydrogen ,..| 307-1 17:8 0°1343 0-7480 
Volume after the combustion .......++«. 2118 18-0 0°2250 0:7480 
Qnd Experiment, June 15. 
Volume of air used ..ccccccsseeeseeees aacael. 1 9S'2 18 02420 0-7476 
Volume after admission of hydrogen ...| 346-4 18 0:0962 07476 
Volume after combustion ..........+- sooeee| 280°2 18 0-1600 0°7476 
3rd Experiment, June 18, with the same air as the last. 
Volume Of air used .....c.ee.e-cevceseerece 231°4 16°4 0°1963 07451 
Volume after admission of hydrogen ...| 822+9 16:2 0°1092 0:7433 
Volume after combustion ........seeesereee 230'8 164 0-1969 0:7410 
4th Experiment. 
Volume of air used ....c.ssccccsccsencevees 214-4 173 0-2305 0°7467 
Volume after admission of hydrogen ...| 313°5 17:3 0-1367 0°7478 
Volume after combustion ........+«.. eeeee| 2343 17-1 0:2224 0:7474 
a 
