292 CLEAN MILK 



"by an expert chemist, who will probably prefer to prepare a norma? 

 alkaline solution from chemically pure sodium carbonate, fused; 

 a normal acid solution of HC1 by titration against this ; and a 

 normal NaOH solution by titration against the normal HC1. 



To prepare a normal HC1 acid solution by titration against the 

 normal NaOH solution, take about ioo c.c. of chemically pure 

 hydrochloric acid (sp. gr. 120) and dilute to 1 litre, making thus 

 a solution slightly stronger than normal. Titrate this against the 

 normal NaOH solution. It will prove to be stronger and the 

 figures obtained will, as described above, for the making of normal 

 NaOH from oxalic acid, indicate how much it should be diluted to 

 make it equal, c.c. for c.c, the strength of the normal NaOH. 

 solution. 



