i 4 4 MILK AND DAIRY PRODUCTS PART 



temperature is constant, arid for butter fat lies between 19 

 and 23 C. 



III. DETERMINATION OF THE CRITICAL TEMPERATURE OF 

 SOLUTION IN ALCOHOL (CRISMER'S METHOD). 



Crismer l has proposed, as a means of testing butter fat, to 

 determine the critical temperature of solution in alcohol. By 

 the critical temperature is understood the temperature at 

 which a mixture of one part butter fat forms or ceases to form 

 a clear solution with three parts by volume of alcohol. 



To carry out this determination test-tubes about 10 mm. in 

 diameter and 100-120 mm. long are used, and they are pro- 

 vided with two marks, the upper one denoting double the 

 volume of the lower. A sensitive thermometer with a very 

 small bulb and opal glass scale is used. The alcohol employed 

 must have a specific gravity of exactly 0'7967 at 15'5 C. If 

 the specific gravity is different, it must be corrected by adding 

 or deducting 0186 for each O'OOOl above or below the specific 

 gravity given above (see also Table IX in Appendix). 



The test is carried out by filling one of the test-tubes to the 

 lower mark with filtered fat, and then with alcohol to the upper 

 mark. With the aid of a cork the thermometer is fitted into 

 the mouth of the tube so that the bulb comes into the middle 

 of the liquid. Afterwards the tube is gently warmed and 

 shaken until a clear transparent solution is obtained. The 

 flame is then withdrawn and the shaking repeated until the 

 liquid begins to get cloudy again, and the temperature is then 

 noted. 



A greater or less degree of acidity affects the result, and 

 causes it to be lower. To prevent this the butter must either 

 be neutralised by treating it with a 10 per cent, solution of 

 potassium carbonate, and then washed with warm water until 

 quite clear, or, as is more usual, the following correction is 

 applied : 



The degree of acidity of the butter is estimated by the 

 number of cubic centimetres of JV/20 potash which are required 

 to neutralise 2 c.c. of butter fat dissolved in 20 c.c. of absolute 



1 Bull. Assoc. Beige des Chimistes, March, 1897 ; Vademecum du Chimiste, 

 Paris, 1903, p. 114. 



