Rural School Leaflet ii6i 



Place the small end of the pipette at the center of the milk and suck 

 the milk up above the 17.6-cc. mark. Quickly place the index finger over 

 the upper end of the pipette, and by releasing the pressure 

 allow the milk to run out until its upper surface is even 

 with the 17.6-cc. mark when the pipette is held straight up 

 and down. 



Place the point of the pipette a short distance into 

 the neck of the test-bottle, holding it against the 

 glass with both pipette and bottle at an angle 

 (Fig. 4). Remove the finger so as to allow the milk 

 to flow into the bottle. Be sure to get every drop 

 of the milk, taking care to drain the pipette and g* 

 to blow the last drop into the bottle. A little 



practice should make any one proficient with the 



■xx Fig. i.— Test- 



Pipette. bottle 



It is best always to make this test in duplicate; 



hence two bottles are needed for each lot of milk. 



Using the acid. — The acid is very strong and must be 



handled with great care. If any gets on the hands, face, or 



clothing, it should be washed off quickly and water should always 



be ready for this purpose. Do not leave the acid where children 



can get it. 



After all the samples of milk to be tested have been measured, 



the acid should be added. Fill the acid measure to the 17.5-cc. 



mark with acid that is between 6o° and 70 F. Pour this into 



the bottle with the milk, holding the bottle in a slanting position. 



The acid will then carry down any milk left in the neck and 



will follow the glass surface to the bottom of the bottle and form 



a layer under the milk. 



Hold the bottle by the neck and give it a cir- 



]r cular motion for a few minutes, mixing the milk and 



p IG the acid until no milk nor clear acid is visible (Fig. 5). 



Pipette,. By this time the contents will be dark-colored and 



measure ^ ot - This change is due to the acid dissolving all 



the solid constituents of the milk except the fat, 



which it does not affect. 



Whirling the bottles. — The bottles are whirled in order to 



separate the fat so that it can be measured. They should f ig . 3 ._ 



be hot when whirled. If necessary they may be heated by Atidmeas- 



standing in hot water before being put into the machine. A 



steam machine is easily kept hot when in use. Other kinds should have 



boiling-hot water placed in them. 



