United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 27. 

 H. W. WILEY, Chief of Bureau. 



COOPERATIVE WORK ON FATS AND OILS, ASSOCIATION OF OFFICIAL 

 AGRICULTURAL CHEMISTS, 1906. 



By L. M. TOLMAN, 



Associate Referee on Fats and Oils. 



I. PROVISIONAL METHOD FOR THE TITER TEST, ADOPTED IN 1905. 



After two years of cooperative work, the following method was recom- 

 mended and adopted by the Association of Official Agricultural Chemists 

 at its meeting November 16-19, 1905, as the provisional method for the 

 titer test : 



METHOD. 



Weigh 75 grams of fat into a metal dish and saponify by using 60 cc of 30 per 

 cent sodium hydrate (36 Baume caustic soda) and 75 cc of 95 per cent by 

 volume alcohol, or 120 cc of water. Boil down to dryness, with constant stirring, 

 to prevent scorching. This should be done over a very low flame or over an 

 iron or asbestos plate. Dissolve the dry soap in a liter of boiling water, and if 

 alcohol has been used boil for forty minutes in order to remove it, adding suffi- 

 cient water to replace that lost in boiling. Add 100 cc of 30 per cent sulphuric 

 acid (25 Baume sulphuric acid) to free the fatty acids, boil until they form a 

 clear, transparent layer, and then wash the fatty acids with boiling water until 

 free from sulphuric acid. Collect the fatty acids in a small beaker and place 

 on the steam bath until the water has settled and the fatty acids are clear, then 

 decant them into a dry beaker, filter, using a hot-water funnel, and dry twenty 

 minutes at 100 C. When dried, cool the fatty acids to 15 C or 20 C above 

 the expected titer and transfer to the titer tube, which is 25 mm in diameter and 

 100 mm in length (1 by 4 inches) and made of glass about 1 mm in thickness. 

 This is placed in a 16-ounce, salt-mouth bottle of clear glass, about 70 mm in 

 diameter and 150 mm high (2| by 6 inches), fitted with a cork, which is per- 

 forated so as to hold the tube rigidly when in position. The thermometer, 

 graduated to 0.1 C, is suspended so that it can be used as a stirrer, and the 

 mass is stirred slowly until the mercury remains stationary for thirty seconds. 

 The thermometer is then allowed to hang quietly, with the bulb in the center of 

 the mass, and the rise of the mercury observed. The highest point to which it 

 rises is taken as the titer of the fatty acids. The titer must be made at about 

 20 C for all fats having a titer above 30 C and at 10 C below the titer for all 

 other fats. 



The fatty acids are tested for complete saponification as follows : 

 Three cc of the fatty acids are placed in a test tube and 15 cc of alcohol (95 

 per cent by volume) added. The mixture is brought to a boil and an equal 

 volume of ammonia (0.96 sp. gr.) added. A clear solution should result, tur- 

 bidity indicating unsaponified fat. 





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