282 E. W. Morley — Yolumetric Compositiwi of Water. 



millimeter- shown in the reading microscope was determined. 



The water was then again stirred, the adjustment at the Jolly 

 point, and the reading of the thermometer and of the reading 

 microscope was repeated. By means of the fine adjustment of 

 the level of the mercury which has been mentioned, the 

 adjustment at the Jolly point could be made within the five 

 hundredth of a millimeter, and it could be repeated as many 

 times as was desired. It was also possible to make the final 

 adjustments, and the two readings, within a time too short for 

 any change of temperature in the gas to be measured. Read- 

 ings of temperature were to the two hundredth of a degree, 

 and of level to the two hundredth of a millimeter. To show 

 what degree of accuracy can be obtained by an apparatus such 

 as is here described, including both errors of readings and 

 errors of transfer due to bubbles of gas entangled in the 

 capillary tube, I put a quantity of gas in a jar in the cistern, 

 transferred it to the eudiometer and measured it, transferred 

 it bach to the jar and measured it again, and so ten times. I 

 give the reduced volumes so found. From this it seems that 

 the probable error of measurement, not including errors of 

 calibration, are something like a seventy-thousandth part of 

 volumes like those used in the determinations of the volu- 

 metric composition of water. I also found the mean error of 

 a single measurement by computation from the mean error of 

 a determination of the ratio sought. In this way, it seems 

 that the mean error of a single measurement of such a volume 

 as one hundred and fifty or two hundred cubic centimeters is its 

 fifty thousandth part. This value includes the errors of cali- 

 bration as far as they affect a determination of the ratio. The 

 direct determination of mean error of measurement was made 

 under selected conditions as to illumination and health which 

 could not be secured in the determinations of the ratio. 



Repeated -measurements of the same volume of gas, transferred 

 to jar after each measurement. 



210-81 cc 210-805 cc 



210-815 210-815 



210-815 210-81 



210-815 210-81 



210-815 210-81 



Determination of nitrogen contained in the hydrogen used 

 for determination of the volumetric co?nposition of water. — 

 The parts p, q, r, were exhausted, filled with hydrogen, from 

 '/i, and again exhausted. The pressure of the gas in n, was 

 then measured by means of m. and its temperature by ther- 

 mometers at n. From this, with the known volume of n, and 



