XXIII. FATS AND OILS. 



1 PREPARATION OF SAMPLE.— OFFICIAL. 



Melt solid fats and filter by means of a hot water funnel or similar apparatus. 

 Make the different determinations on samples of this melted, homogeneous mass. 

 Filter oils that are not clear. Keep oils and fats in a cool place and protected from 

 light and air, otherwise they will soon become rancid. Weigh out at one time as 

 many portions as are needed for the various determinations, using a small beaker 

 or weighing burette. 



SPECIFIC GRAVITY. 

 . 20°C. ^ . .. 



20 °C 

 Determine the specific gravity of the oil at -^ by means of a pycnometer. 



If the specific gravity of the oil is determined at other than standard tempera- 

 ture, the approximate specific gravity at 20°C. may be calculated by means of the 

 following formula: 



G = G' + 0.0007 (T-20°C.) in which 

 G = specific gravity at 20°C.; 



T°C 

 G' = specific gravity at -^ ; 



T = temperature at which the specific gravity was determined; 

 0.0007 = mean correction' for 1°C. 



At the Temperature of Boiling Water.— OflBciaL 



3 STANDARDIZATION OF FLASKS. 



(a) Fill a tared, 25-30 cc. specific gravity flask with freshly boiled, hot water. 

 Place in a briskly boiling water bath for 30 minutes, replacing any evaporation 

 from the flask by the addition of boiling water. Then insert the stopper, previous- 

 ly heated to 100°C., remove the flask, cool and weigh. 



(b) The following formula may be used for calculating the weight of water (W^) 

 which a given flask will hold at T° (weighed in air with brass weights at the tempera- 

 ture of the room) from the weight of water (W*^) (weighed in air with brass weights 

 at the temperature of the room) contained therein at t°: 



W^ = W* ^ [1 + 0.000026 (T - t)] in which 



d' 

 d'^ = the density of water at T°; 

 d* = the density of water at t°. 



4 DETER.MINATION. 



Fill the flask, dried at the temperature of boiling water, with the dry, hot, freshly 

 filtered fat, which should be entirely free from air bubbles; keep in the water bath 

 30 minutes at the temperature of boiling water. Insert the stopper, previously 

 heated to 100°C., cool and weigh. Divide the weight of contained fat by the weight 

 of contained water previously found to obtain the specific gravity. 



The weight of water at boiling temperature must be determined under the baro- 

 metric conditions prevailing at the time the determination is made. 



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