128 



COMPOSITE SAMPLES 



Corrosive sublimate is a strong and a very satisfactory 

 preservative; but it is quite poisonous, and where the powder 

 itself, which is white, is used in composite samples some kind of 

 coloring matter should always be added to indicate its presence. 

 According to the authors' experience, corrosive sublimate 

 tablets can be highly recommended. The tablets contain a 

 color, which, when dissolved, colors milk, so that it can readily 

 be distinguished as not being fit for human food. The tablets are 



very poisonous, but are more 

 efficient in their preservative 

 effect than bichromate of 

 potash. They can be ob- 

 tained from any creamery- 

 supply house. 



During the winter, when 

 the samples are kept com- 

 paratively cold, less perserva- 

 tive is needed than in the 

 summer. One corrosive sub- 

 limate tablet will keep a 

 half-pint to a pint of milk 

 or cream in good condition for about two weeks in summer, 

 and about three weeks in winter, providing the sample is properly 

 cared for. Some makers are practicing testing at the end of 

 every month during the winter, and every two weeks during the 

 summer. Testing at the end of every month saves labor, but it 

 is not a reliable method to follow under all conditions, as some of 

 the samples are likely to be somewhat impaired after standing 

 so long. 



Arrangement of Composite Samples. Pint glass jars with 

 covers are, so far as known, the most convenient vessels to use 

 for composite samples. Shelves should be arranged in the weigh- 

 ing-room on which to keep the bottles. If possible, it is best 

 to have them in a case closed with glass sliding doors. This 

 is neat, and, if the glass doors fit well, the samples are in some 

 measure protected in case of quick, unexpected changes in tem- 

 perature. These sliding doors should be locked when the cream- 



FIG. 41. Composite samples and rack to 

 hold sample jars. 



