BUTTERMILK. 203 



There remains still a little carbon dioxide dissolved ; this can 



N 

 be estimated by titrating a weighed amount with baryta 



water, using phenol- phthalein as indicator ; the difference between 

 the acidity thus estimated and that estimated as previously 

 described will represent, without great error, the carbon dioxide 



(1 c.c. ^ alkali = 0-0022 gramme C0 2 ). This should be added 



to the amount estimated by absorption. 



Buttermilk and whey are analysed by the methods given 

 for milk ; the total proteins of whey cannot be determined by 

 Ritthausen's method, and the total nitrogen must be estimated. 



Estimation of Water and Salt in Buttermilk. It 

 happens sometimes that when churning both salt and water 

 find their way in the buttermilk ; when the buttermilk is to be 

 sold, it is important to be able to estimate rapidly both the 

 proportion of water and of fat. 



It was found that chlorides could be titrated in milk with 



N 



r-- silver nitrate solution, using potassium chromate as indicator, 



N 

 and that 10 c.c. of milk took on an average 3-45 c.c. silver 



solution, with extremes of 3-35 c.c. and 3-6 c.c. in nine samples. 



N 

 It was further found that the number of c.c. of = silver solution 



for 10 c.c. of milk could be deduced with considerable accuracy 



N 

 by multiplying the aldehyde figure (obtained with strontia) 



by 0-171, and subtracting this quantity from the quantity actually 

 used ; the remainder was a measure of the sodium chloride. 



A series of determinations showed that 1 gramme of sodium 

 chloride added to 100 c.c. of milk raised the density by 0-00735, 

 and by multiplying the amount of salt found by this figure the 

 increment of density due to the addition is deduced, and sub- 

 tracting this from the density found, the density of the milk is 

 obtained. From this last figure and the fat the solids not fat 

 can be calculated, and from this the amount of added water 

 roughly deduced. 



The method is : Estimate the specific gravity, fat, and alde- 



N 

 hyde figure as usual ; titrate 10 c.c. of buttermilk with silver 



nitrate, using potassium chromate as indicator, till a reddish 

 colour is produced. From the volume of silver nitrate used 

 subtract the aldehyde figure X 0-171, and multiply the residue 

 by 0-0585, the product being the percentage of salt ; multiply this 



