MEASUREMENTS 



45 



Shake or swirl until the solute is dissolved and then add water up to the 

 line on the neck. Finally, pour the solution into an Erlenmeyer flask for 

 storage. Please do not store solutions for long periods in volumetric 

 flasks. 



The graduated cylinder (Fig. 4-6) is the convenient piece of glass- 

 ware for rapid measurements of quantities of liquid. Since the diameter 

 is greater, relatively, than that of any other volumetric item, an error in 

 height of liquid means a greater volume error. 



Fig. 4-6. Several graduated cylinders. (Courtesy Corning Glass Works.) 



Calihration: This is a procedure for assigning values to the various 

 graduations on the glassware. Ordinarily the calibration is performed 

 by the manufacturer. Volumetric glassware is calibrated either "to con- 

 tain" or "to deliver." The difference is the film of water that adheres 

 to the glass after delivery. That is, a pipette might contain exactly 10.01 

 ml, but only 10.00 ml would flow out, or be delivered. Burettes and 

 pipettes are almost always calibrated "to deliver." Volumetric flasks usu- 

 ally are calibrated "to contain." Graduated cylinders might be calibrated 

 either way. The manufacturer indicates on the glassware how it was 



