DAIRY HUSBANDRY 
49 
SERIES G. 
Testing Milk for Casein. 
Materials necessary for 10 students: 
*1— Hart casein centrifuge ( 15 " diameter, tubes extended). 
*20 — Hart casein test bottles. 
5—20 cc. pipettes. 
5—10 cc. pipettes. 
5—5 cc. pipettes. 
5—1 cc. pipettes. 
*100 cc. — Chloroform. 
*500 cc.—.25 % acetic acid solution (10 cc. glacial acetic acid diluted to 
100 cc. with water: then diluting 25 cc. of this solution to 
1000 cc). 
5—200 cc. flasks. 
*500 cc.—Standard NaOH solution (795 cc. n /io NaOH solution plus 
distilled water to equal 1000 cc). 
*25—Filter paper discs 6". 
*500 cc .— n / 9 NaOH solution. 
*200 cc. — 40% formaldehyde (neutral). 
3000 cc—Distilled water. 
5 — 4" glass funnels. 
EXERCISE NO. 36 
Object: To become acquainted with the Hart Casein Test. 
Procedure: The casein content of milk averages between 2.0 and 4.0%, 
and is equal to about 80% of the proteins present. Its per¬ 
centage composition is approximately, carbon 53.0%; hydro¬ 
gen 7.12%; nitrogen, 15.65%; oxygen, 22.6%; Sulphur, 
0.78%; phosphorous, 0.85%. It forms about 20-25% of the 
total solids of milk. The ratio of casein to fat varies from 
1:1.9 to 1:1.3. 
Observe the table given below: 
Breed Authority Casein Fat 
Holstein.(Hart. 1 : 1.49 
) Eckles & Shaw. 1 : . 1.31 
Ayrshire.(Hart. 1 : 1.44 
'.Eckles & Shaw. 1 : 1.36 
Jersey.jHart. 1 : 1.72 
\ Eckles & Shaw. 1 : 1.69 
Guernsey. Hart. 1 : 1.90 
Shorthorn. Eckles & Shaw. 1 : 1.36 
A. Test each of the lots of milk provided in duplicate as follows: 
(1) Measure 2 cc. (up to the 4% mark) of chloroform into a 
Hart casein test bottle. Add 20cc. of the prepared .25% 
acetic acid solution at room temperature. Add 5 cc. of the 
well mixed sample of milk. Hold thumb over opening of 
bottle and shake carefully for 20 seconds. Place bottles 
