ISO 



eules, by hyroloysis either with an acid or ferment into peptones, etc. Then 

 we would expect the Formol number to increase, double, if each protein 

 molecule were split into two simpler ones. This is true, bo formol titration 

 gives a measure of the hydrolytie cleavage. We know thai the proteide of 



milk are neutral to indicators, but on the addition of the formaldehyde 

 become decidedly acid to these indicators. 



Now if we can determine a factor or equivalent of the acidity produced 

 on the addition of the formaldehyde to milk proteide, we can at once deter- 

 mine the percent of proteids in milk by titrating the acidity with a standard 

 alkali. 



In 1912, E. Holl Miller, of England, worked out a method for estimating 

 the proteids in butter, and the same method is used in determining the 

 proteids in milk. 



Directions for estimating the -proteids in butter. Weigh into a tared beaker 

 exactly 10 grams of butter, which is placed in a water bath at 60 c to 70 < '. 

 until the butter is completely melted. Twenty-five ec. of carbon dioxide 

 free water is then added at about 60° C. and 1 cc. of phenolpthalein solution. 

 The contents are well agitated. Run in * XaOH until a faint permanent 

 pink color is formed. It is found that the end point is masked by the yellow- 

 color of butter fat, the contents of the beaker should be allowed to settle 

 and the bottom aqueous layer observed, and the addition of alkali continued 

 until the pink tint is obtained. Five cc. of formaldehyde (40 per cent.) is 

 added. The formaldehyde must either be neutralized before addition or its 

 acidity equivalent for 5 ec. obtained and afterwards deducted. After the 

 formaldehyde has been added the beaker is well shaken and again ^ XaOH 

 run in until a permanent faint pink color is produced in the aqueous layer. 

 The number of ce.^ alkali used in the second titration less the amount 

 equivalent to the acidity of the formaldehyde. Xo deduction is necessary 

 if the formaldehyde was neutralized before being added to the butter. Now 

 the number of cc. ^ alkali used to neutralize the acidity produced on the 

 addition of the formaldehyde is proportional to the protein present. One 

 ec. of *i alkali is equivalent to .01355 grams of protein nitrogen or .0864 

 grams milk protein, assuming a definite proportion of casein and albumen. 

 Then to calculate the percent of protein wc have ' ~To~ i = P er " 

 cent protein if 10 grams of butter were taken. 



