APPENDIX. - 383 



V— the required volume at standard temperature, 0° C, and 760 mm. Hg. 



V^ = the volume at the observed temperature and pressure. 

 h = the observed pressure. 



a = the coefficient of expansion, which is a constant (,003665). 

 t = the observed temperature. 



The formula is obtained as follows : — 



With reference to the correction of the given volume for temperaiwn •• 



l+at: I :: VI :V 

 V^ 



and for pressure : 



■vat 



l-Vat 



hi 760 



760 {i+at) 



Example. — Suppose the volume of gas to be corrected for temperature and 

 pressure, i.e., V^ = 30 cc, the observed barometric pressure, i.e., ^=-740 mm., 

 and the temperature of the room, i.e., t^-is" C, then the required volume 

 will be : 



_, 30 X 740 22200 - 



760 ( I +.003665 X 15) 801.78100 '* 



».«., 30 CC. of a gas at 740 mm. pressure and 15° C. are reduced to 27.6 cc. at 

 standard pressure and temperature (760 mm. and 0° C). 



SOLUBILITIES IN WATER AT 15* to i8' C. 



Ammonium chloride, 36 per 100. 



Sodium chloride, 3^ >> f» 



Ammonium sulphate, 5° f» i» 



Magnesium sulphate 125 „ „ 



IV. 

 RECORDING APPARATUS. 



There are many forms of recording apparatus in use, and some of them are 

 described in the text (Lesson XXXIV.). When a number of students have to 

 be taught to record graphically the results obtained in an experiment, then 



