MANUAL OF GENERAL AGRICULTURE. 105 



rain water. Make a liberal reading as in the case of milk. 

 Some difficulty may be encountered in getting the smaller 

 amount of fat within the scale. This may be overcome 

 by putting a cork into the neck of the large opening and 

 gently working it up and down so that it will be possible 

 to regulate the position of the fat. Make a reading as 

 quickly as possible or the fat may adhere to the inside of 

 the neck as a film of grease which cannot be measured by 

 the scale. A test of .02 of one per cent shows an efficient 

 separation. 



A test of skim milk showing no fat in the neck of the 

 test bottle on completion of the test generally shows poor 

 work on the part of the operator and should be repeated. 



Obtain some butter milk and also some whey and 

 test each the same as skim milk except that in the case 

 of whey 17.5 c.c. of acid is sufficient since whey contains 

 less solids not fat for the acid to dissolve. 



78. THE LACTOMETER AND ITS APPLICATION. 



Materials: Quevenne lactometer, 500 c.c. cylinder, 

 pint of milk, pint of skim milk. 



The specific gravity of normal cow's milk will vary 

 in different samples between 1.029 and 1.035 at 60 degrees 

 F., the average being about 1.032. The lactometer is 

 used for determining the specific gravity of milk. There 

 are two in use : the Quevenne and the Board of Health. 

 Only the Quevenne will be considered. 



The Quevenne lactometer consists of a hollow cylinder 

 weighted by means of mercury so that it will float in 

 milk in an upright position, and provided with a narrow 

 stem at its upper end, inside of which is found a grad- 

 uated paper scale. A thermometer is placed in the cylinder 

 with its bulb at the lower end of the lactometer and its 

 stem rising above the lactometer scale. The scale is 

 marked at 15 and 40, and divided into 25 equal parts, 

 with figures at each five divisions of the scale. The single 

 divisions are called degrees. The fifteen degree mark 

 is placed at the point to which the lactometer will sink 

 when lowered into a liquid of a specific gravity of 1.015 



