$2 DAIRY ANALYSIS 



Baryta Solution. Dissolve 33-35 grammes of 

 barium hydrate in 2 litres of water ; allow to settle, and 

 store in a bottle fitted with a soda lime tube to prevent 

 access of C0 2 . Check the strength by titration (see p. 94). 



Caustic Soda. See Soda. 



Fehling's Solution. Copper sulphate solution: Dis- 

 solve 34.639 grammes of crystallised copper sulphate 

 in water, and make up to 500 c.c. Alkaline tartrate 

 solution : Dissolve 173 grammes of pure sodium 

 potassium tartrate (Rochelle Salt), and 51 to 55 grammes 

 of sodium hydroxide of good quality in water, and make 

 up to 500 c.c. 



Hydrochloric Acid -. Dilute 50 c.c. strong hydro- 

 chloric acid to i litre ; ignite a quantity of pure sodium 

 bicarbonate at a dull red heat, and cool in a desic- 

 cator ; weigh (accurately to i milligramme) portions of 

 this, of about i gramme each, dissolve in water, add 

 a little methyl orange, and run in the hydrochloric acid 

 solution from a burette till the sodium carbonate solu- 

 tion turns pink ; the solution should be covered as much 

 jas possible with a watch-glass to prevent loss by spirting 

 as the C0 2 is given off. Wash the watch-glass into the 

 solution, and boil it, and continue the titration till the 

 pink colour is permanent on boiling. It is well to 

 place a beaker containing an equal bulk of distilled 

 water, and the same volume of methyl orange solution, 

 and one drop (0.05 c.c.) of hydrochloric acid, and titrate 

 till the sodium carbonate solution has the same colour, 

 and subtract 0.05 c.c. from the quantity of acid used. 



If the solution is , 20 c.c. should be required for 



each 0.53 grammes of sodium carbonate ; if this quantity 

 is not used dilute in the proportion of the quantity used 

 to 20 c.c. , or use the solution as it is, and multiply by 

 20 divided by the quantity used to obtain its value in 



terms of acid. solution is made from solution 

 2 10 2 



by diluting 200 c.c. to i litre. 



