WITH A LIQUID OF DENSITY 1.01 ( 2 ) . THIS VESSEL IS SEALED IN A FLAME . ITS OUTSIDE CAPACITY SHOULD BE EQUAL TO THE OUTSIDE CAPACITY OF THE FILLED PYCNOMETER TO WITHIN 1 ML .
TARING OF THE PYCNOMETER
THE EMPTY PYCNOMETER SHALL BE TARED USING A BALANCE WITH A SENSITIVITY OF 0.1 MG AND A MAXIMUM RANGE OF AT LEAST 200 G , USING PRECISION WEIGHTS .
ADD THE MASS OF AIR CONTAINED IN THE EMPTY AND DRY PYCNOMETER ( 3 ) TO THE WEIGHTS , P , PLACED BESIDE THE PYCNOMETER . THE CORRECTED TARE OF THE EMPTY PYCNOMETER IS THUS OBTAINED .
1.2 G PER LITRE MAY BE ASSUMED AS THE DENSITY OF AIR ( 4 ) FOR THE CALCULATION OF THE MASS OF AIR M CONTAINED IN THE PYCNOMETER .
THE MASS OF THE AIR M CONTAINED IN THE APPARATUS IS OBTAINED BY MULTIPLYING THE VOLUME OF THE PYCNOMETER IN MILLILITRES BY 0.0012 . AS IT IS NOT NECESSARY TO KNOW M WITH AN ACCURACY GREATER THAN TO THE NEAREST 0.5 MG , THIS VOLUME IS NUMERICALLY EQUAL TO P - P' , P' BEING THE WEIGHT REQUIRED TO BALANCE THE PYCNOMETER FILLED WITH WATER .
TARE THE WATER-FILLED PYCNOMETER AT T* C , T BEING THE TEMPERATURE AT WHICH THE OPERATION IS CARRIED OUT AS SHOWN ON THE PYCNOMETER THERMOMETER , MEASURED TO 0.02* C , AND P' BEING THE WEIGHT IN GRAMS REQUIRED TO ESTABLISH EQUILIBRIUM .
CALCULATE THE VOLUME OF THE PYCNOMETER AT 20* C ( 5 ) BY MULTIPLYING THE MASS OF WATER AT T* C CONTAINED IN THE PYCNOMETER AT T* C BY THE FACTOR F GIVEN IN TABLE I . THIS TABLE GIVES THE RECIPROCALS OF THE DENSITIES OF WATER AT T* C CORRECTED FOR THE EXPANSION OF THE PYREX PYCNOMETER BETWEEN T AND 20* C .
THE KNOWLEDGE OF THIS VOLUME IS NECESSARY FOR THE MEASUREMENT OF THE DENSITIES OF LIQUIDS .
IF THE SPECIFIC GRAVITY IS TO BE CALCULATED , IT IS NECESSARY TO KNOW THE MASS OF THE WATER AT 20* C CONTAINED IN THE PYCNOMETER AT 20* C . THIS IS OBTAINED BY MULTIPLYING THE VOLUME AT 20* C BY 0.998203 , THE DENSITY OF WATER AT 20* C .
THE CALIBRATION OPERATION SHOULD BE CARRIED OUT IN TRIPLICATE TO CHECK THAT THERE IS NO ERROR IN THIS FUNDAMENTAL OPERATION ( 6 ) .
THE TARE OF THE EMPTY PYCNOMETER AND THE VOLUME AT 20* C ( AND CONSEQUENTLY THE MASS OF THE WATER AT 20* C ) ARE CHARACTERISTIC OF THE EQUIPMENT . BECAUSE A TARE OF THE SAME VOLUME AS THE FULL PYCNOMETER IS USED IT IS NOT NECESSARY TO DETERMINE THEM AT EACH MEASUREMENT . IT IS RECOMMENDED , HOWEVER , TO CHECK THEM PERIODICALLY E . G . ANNUALLY .
TABLE I
F FACTORS
BY WHICH THE MASS OF THE WATER CONTAINED IN THE PYREX PYCNOMETER AT T* C HAS TO BE MULTIPLIED TO CALCULATE THE VOLUME OF THE PYCNOMETER