6 SMALL WATER SUPPLIES. 



3. To test for the presence of carbonic acid, add 

 lime water (liquor calcis) to the supply, and a milky 

 solution will result. The lime water may be made 

 from slaked lime and water, the solution containing 

 half a grain of oxide of lime (CaO) to the ounce. 



4. To find out if sulphur is present, allow some 

 mercury to stand in the water, when its presence 

 will cause a dark surface to appear on the otherwise 

 silvery mercury. 



5. Lime in solution will cause a milky precipitate 

 on the addition of oxalic acid. 



6. Sulphate of lime. The addition of barium chlo- 

 ride causes a white precipitate. 



7. The presence of alkalies (which will neutralize 

 any acid present) will turn litmus paper blue if it has 

 been reddened by dipping in an acid solution, such 

 as vinegar, beforehand. 



8. To test for the presence of iron, add a solution 

 of potassium ferrocyanide to the water, which will 

 cause the natural blue colour of the ferrocyanide to 

 disappear. 



9. The presence of lead will cause a black dis- 

 colorization when ammonium sulphide solution is 

 added to the water. 



10. The presence of magnesia (which is of more 

 importance in boiler-feed water than domestic sup- 

 plies) is proved on boiling the water and adding am- 

 monium carbonate and phosphate of sodium. The 

 result will be a white precipitate of magnesia. It 

 may here be stated that too much hardness in water, 

 besides being a commercial disadvantage, is also very 

 unpopular amongst domestic users. The principal 

 cause is the presence of bicarbonate of lime. It is 



