144 AGRICULTURE 



tion has been reached an indicator is required. 

 For this purpose a chemical substance called 

 phenol phthalein is used. It is colourless in 

 acid and pink in alkali. The greater the degree 

 of acidity present the more soda solution will 

 be required to produce the pink colour that 

 is to effect the neutralisation, and vice versa. 

 For the use of the acidimeter we require : 



(1) Standard solution of caustic soda. Soda 

 is generally used, but any alkali, such as 

 potash, lime, magnesia would do. By 

 standard solution is meant a solution of 

 which a known quantity will neutralise a 

 definite amount of acid. In this case the 

 standard solution is of such strength that one 

 cubic centimetre neutralises .01 grammes, or 

 looth part of a gramme, (i gramme equals 

 the weight of i cubic centimetre of distilled 

 water, at 4 C. i cubic centimetre equals the 

 loooth part of a metre.) 



(2) Ten cubic centimetres milk or whey, or 

 whatever is to be tested ; in all estimations 

 ten cubic centimetres are used. 



