PRESERVATIVES FOR SAMPLES 315 



the fat is worth 30 cents a pound it would amount to $4.05, or 

 approximately $8 a month. If there are 75 such patrons, $600 

 per month may easily have been paid out to the farmers for milk 

 fat which was never delivered. This is one reason why some 

 creameries have great difficulty in maintaining" an adequate or 

 even reasonable over-run. The sample must not only have been 

 thoroughly taken, but also have been protected from evaporation 

 of water or mechanical loss of fat in order to be of exact value. 



Preservatives for Samples. — In order that it shall not be 

 necessary to test the milk immediately nor to test every milking, 

 preservatives have been brought into use for the purpose of keep- 

 ing the milk sweet. All milk preservatives are poisonous, other- 

 wise they would not destroy the bacteria and preserve the milk. 

 The best preserving substance to use is corrosive sublimate, made 

 up in tablet form, with the addition of coloring matter. The 

 preservative itself is colorless. The coloring matter is added to 

 insure safety. Tablets of this sort may be procured from any of 

 the dealers in creamery supplies. 



Potassium bichromate in powdered form is absolutely not 

 to be recommended for general use. It unites with and increases 

 the strength and action of the acid and since it is extremely 

 difficult to measure the powder with sufficient accuracy to get 

 exactly the same quantity into each sample bottle, the tester will 

 later be unable to know how much acid to add to secure the 

 desired effect. This substance is now put up in tablet form, 

 which increases the ease with which it may be used and makes of 

 it a fairly satisfactory preservative. Care must be exercised, 

 however, in the addition of the acid to the sample that a quantity 

 less than usual is added, and that there is near at hand some 

 warm water to be added if necessary to check the burning process. 



Formaldehyde is the safest of all the preservatives to use, 

 since it gives off a violent and disagreeable odor, and therefore is 

 not likely to be consumed, and not being a violent poison would 

 not likely cause disastrous results if it were accidentally fed 

 to pigs or calves. The chief objection to its use is the fact that 

 it seems to toughen the casein in the milk and render the thor- 

 ough digestion by the acid difficult. It is necessary to use more 



