13. Two large earthenware crocks, one in which to empty the 

 test bottles, and the other containing a strong solution of wash- 

 ing soda for cleaning the bottles. 



14. A set of suitable brushes for cleaning test bottles. 



15. A 500 c.c. graduated measure, reading 5 c.c. 



16. A 100 c.c. graduated measure reading c.c. 



17. A stock of sulphuric acid and amyl alcohol. 



18. A reliable chemical thermometer (centigrade). 



A careful manager will always see that he has the most indis- 

 pensable of these articles in duplicate, particularly the pipettes 

 and burettes which are liable to be broken. 



The sulphuric acid should be of the quality known as " best 

 white commercial," and should have at 15 C. a specific gravity 

 of from 1-820 to 1-825. The former strength is used in 

 summer, and the latter in winter. About a dozen Winchester 

 quarts of the acid should be purchased at a time ; it must be 

 kept in stoppered bottles, as it loses strength if exposed to the 

 air. If strong acid of specific gravity 1 840 has been pur- 

 chased it must be diluted with water as follows : 1 part of 

 water to 10 parts of acid for summer use, and 1 part of water 

 to 12 parts of acid for winter use. Great care must be taken in 

 diluting the acid. The best method is to take two litres, that 

 is, 2,000 c.c., in a Winchester quart bottle, and to add thereto 

 the necessary amount of water in small quantities at a time, 

 taking care to shake the bottle after each addition. If all the 

 water is added at one time the mixture will suddenly become 

 very hot, and may crack the bottle. It is not necessary to have 

 the temperature exactly 15 C. for testing the specific gravity, 

 as any deviation from this temperature can be easily allowed for 

 by adding or deducting- '001 from the hydrometer reading for 

 each degree above or below 15 C. 



For testing separated milk or buttermilk a weaker acid than 

 the above should be used. An acid of about the proper strength 

 may be made by adding one part of water to either 55 parts of the 

 1 820 strength, or to 9 parts of the 1 840 strength. A very good 

 indication that the strength of the acid is correct is afforded by 

 the pale lemon colour which the fat in the neck of the test bottle 

 then assumes. If the fat is very dark the acid is too strong, 

 whereas if the fat is white and has beneath it particles of undis- 

 solved curd the acid is too weak. 



The amyl alcohol (commonly known as fusel oil) should have 

 a specific gravity of -815 or -816 at 15 C., and should boil at 

 1269-130 C. It should be colourless and free from fat. Its 

 purity in this respect may be tested by mixing equal parts of it 

 and hydrochloric acid and whirling 22 c.c. of the mixture in 

 a test bottle in the centrifuge. Any fat present will collect in 

 the neck of the test bottle ; but owing to its pale colour a very 



