An Apparatus for Determining the Compositions of Solutions ,An evaporation apparatus was constructed from a. Pyrex or a Kimax beaker and glass fritted crucible. A side arm was added for filling. I t has been found by use of these vessels that analysis of relatively concentrated solutions can be made to a high degree of accuracy and precision. The size of the evaporation apparatus depends on the amount of solution that needs to be evaporated in order to give good results. Usually it is made large enough to give st least 1 g of solute after volatization of the wlvent of the solution through the frit. This method is very useful for salts in solution where there is not any convenient method of analysis. Also it is good for solutions that tend to splatter when evaporated by normal procedures. The evaporation can be carried out in a vacuum oven or a heated vacuum desiccator. A boiling chip placed in the vessel aids in the evaporation. The degree of fineness of the glass frit depends upon the volatility of the sample. I t was observed that coarse frits gave good results and decreased the time necessary for evaporrttion. The figure shows the construction of the evaporation apparatus. Table 1 gives appropriate sizes of
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Table 2.
S~ODD.~
.....
Actual concentration (g solute/g solution)
Data for Sodium Perchlorate in Aqueous Solutions
Determined concentration (g solute/Number of g solution trials
Standard deviation of determined value
Table 1 . Appropriate .. . Sizes of Equipment
Capacity (ml) 20 50 100 Crucible size (ml) 15 30 50 Beaker size (ml) 20 50 100
crucibles and beakers for a given capacity. Table 2 shows some data for sodium perchlorat,e in aqueous solutions which were made up by weight and corrected to vacuum.
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Journal o f Chemical Education
