Physical Properties of Water 279 



20 c.c. of ether, and into the third pour 20 c.c. of olive 

 oil. Securely stopper each vessel and shake them well. 

 Allow each, after shaking, to remain undisturbed for 

 some time. Note whether any separation of the liquid 

 mixture into two layers occurs. Read off the number 

 of c.c. in the upper layer, should this happen. Sub- 

 tracting the values thus obtained from 20 c.c. the 

 volume originally used will provide a rough idea of 

 the amount of liquid dissolved by 100 c.c. of water in 

 each case. 



QUESTIONS 



1. Make a list of all the properties of water dealt with in Chapters 

 i to xvi. 



2. What methods would you employ to obtain, (a) a sample of 

 clear water ; (6) a sample of pure water, from some muddy river- 

 water ? How would you make certain that the latter sample was 

 really pure water ? 



3. One kilogram of water from the Irish Sea was shown by 

 analysis to contain 26 '43 g. of common salt. The specific gravity 

 of the water at 15 was 1*02484. What weight of salt would be 

 contained in the residue left on evaporating 100 litres of the water ? 



4. 20 g. of a substance were shaken for 30 minutes with 100 g. 

 of distilled water. The resulting liquid was filtered and 20 g. of the 

 filtrate on evaporation to dryness left a residue weighing 2 '74 g. 

 Find the percentage solubility of the substance, i.e. the weight of 

 it which will dissolve in 100 g. of water. 



5. Suggest possible reasons for the direction in the text that 

 the first portion of each distillate should not be preserved. 



6. Devise a method of finding out whether sodium thiosulphate 

 ("hypo") will form a supersaturated solution. 



7. Describe in full the method you would adopt in order to 

 obtain large crystals of washing-soda. 



