Detecting Dissolved Solids & Solvent Recovery in Lab

Codynn
3 Min Read
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THEORY:

Distillation is the process of converting a liquid into its vapour by the application of heat, and then condensing the vapour into the same liquid by cooling.

That is, vaporization + condensation makes distillation. Hence the process of distillation can be employed to recover a solvent from a solution containing dissolved solids.

APPARATUS :

1) Distilling flask 

2) Liebig’s condenser 

3) Conical flask

4) Rubber tubing 

5) Stand and clamps 

6) Water trough

7) Clock glass

8) Beaker

9) Tripod stand and wire gauze.

CHEMICALS:

1) Impure water containing some NaCl, CuSO4 etc.

 PROCEDURE:

A. Tests for dissolved solids

Perform the detection and the tests for the dissolved solids as follows.

ExperimentObservationInference
i)  Evaporate a little of thegiven sample on a clockglass kept over a beakerhalf filled with waterSolid residue left on theclock glassPresence of dissolvedsolids
ii) A little sample + 2 dropsAgNO3Curdy white ppt White pptPresence of chloride
iii) A little sample + 2 dropsBaCl2White pptPresence of solublecarbonates or sulphates.
iv) Test the sample withblue and red litmusi) turns blue litmus red.ii) turns red litmus bluei) acidic impuritiesii)  basic impurities

B. Distillation

a. Assemble the apparatus as shown in the figure 2.4 (a)

b.Take the given solution in the distilling flask, and heat it over the wire gauze by means of the Bunsen flame till it boils. The solvent vaporized, and is gradually condensed back to the liquid state as it passes through the Liebig’s condenser which is kept cool by the circulation of water. The condensed liquid trickles down, and is collected inside the receiver. The pure liquid thus collected in the receiver is called the distillate.

c.Use the first portion of the distillate to wash the receiver, and reject it into the sink.

d. Collect the subsequent portions of the distillate, and repeat the above tests with small samples of the distillate.

N.B. In case, the distilling flask and condenser are not available, a glass retort as shown in fig. 2.4 (b).

Or

A conical flask with a side tube as shown in fig 2.4 (c) may be used for simple distillation.

Tests for the Purity of the Distillate:

ExperimentObservationInference
i)  Evaporate some distillate on a clock glass as beforeNo solid residueAbsence of dissolved solids
ii) A little sample + 2 drops of AgNO3No pptAbsence of chloride
iii)  A little sample + 2 drops of BaCl₂No pptAbsence of soluble carbonates or sulphates
iv) Test the distillate withblue and red litmusNo effect on thelitmus papers.The distillate is neutral.

Separation of Two Immiscible Liquids

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