17 , 2 
Adriano: Determination of Lactose 
217 
per sulphate 2 solution and 8.8 cubic centimeters of 0.5 sodium 
hydroxide solution. After the addition of the alkali the mixture 
must still have an acid reaction and contain copper in solution. 
Fill the flask to the 500 cubic centimeter mark; mix, filter 
through a dry filter, and determine the lactose in the filtrate, 
taking 50 cubic centimeters for the copper reduction and 10 
cubic centimeters for the alkaline potassium permanganate 
method. 
For the optical method the directions given in Sherman’s 
Organic Analysis (9) were followed. 
The results of the analysis performed on canned and on fresh 
cows’ milk are as follows: 
Table 3 . — Determination of lactose in milk. 
[Figures express the percentages of lactose by weight.] 
Sample. 
Lactose. 
No. 
Description. 
Polaris- 
cope. 
Quisum- 
bing’s 
method. 
Soxhlet's 
method. 
1 
Per cent. 
4. 60 
Per cent. 
5.21 
Per cent. 
5.65 
2 
Do__ 
4.66 
5. 20 
6. 64 
4. 680 
6.205 
5. 645 
8 
6.12 
9.52 
9.76 
a 4 
Do 
8.26 
9. 88 
10. 08 
*6 
Do 
7.28 
9.70 
9. 88 
*6 
Do 
7.22 
9. 84 
9.86 
7. 220 
9.735 
9.895 
7 
8.71 
9. 98 
10. 30 
8 
Do 
8. 78 
9. 99 
10. 24 
9 
Do 
8.72 
9. 94 
10. 30 
10 
Do. - 
9.94 
10.29 
8.736 
9.962 
10. 282 
11 
4.41 
4.50 
4.52 
12 
Do 
4.42 
4.46 
4. 62 
13 
Do 
4.38 
4. 63 
4.46 
14 
Do 
4.38 
4.46 
4.73 
4.395 
4.487 
4.582 
15 
4. 50 
4.80 
5.08 
16 
Do - 
4. 48 
4.79 
5.06 
4.490 
4. 795 
5.070 
a These samples were taken from the same can as No. 3, but they were treated with varying 
amounts of pure lactose. The percentage of lactose added was subtracted to find the true 
percentage of lactose in the milk. 
a Dissolve 34,639 grams of copper sulphate in 100 cubic centimeters of 
water and dilute to 1 liter. 
