SPECIFIC GRAVITY OF WHEAT AKD OTHER CEREALS. 5 



disconnected from the pump and completely filled with toluene 

 cooled to about 18° C. The thermometer is then placed tightly in 

 the neck of the bottle and the temperature of bottle and contents 

 allowed to rise gradually to exactly 20° C. The last drop on the 

 end of the capillary tube is removed with a piece of filter paper, the 

 overflow cap set firmly in place, and th(^ picnometer and contents 

 weighed on a good analytical balance. 



The specific gravity of the sample is calculated according to the 

 following fonnula: 



I Specificgravityof the toluene X weight of the wheat. 

 Specific gravity of the wheat= height of the toluene displaced by the wheat. 



For example, if the weight of the picnometer containing toluene and 

 the 10 grams of wheat is 87.2697 gi'ams and the weight of the pic- 

 nometer containing toluene alone is 83.44G1 grams, then by sub- 

 tracting the latter figure from the former we have 3.8236 grams, and 

 this subtracted from 10 gives 6.1764, which is the weight in grams of 

 the toluene displaced by 10 grams of wheat. Substituting in the 



0.8667X10 , ^^^^^ ,, .^ 



formula given above, we have q if^l — = 1-4032, the specihc gravity 



of the wheat. 



ADVANTAGE OF USING TOLUENE. 



Toluene has been found most satisfactory for specific-gravity deter- 

 minations, there being little tendency for this substance to soak into 

 the kernels, as is the case with water and alcohol. After standing 

 several hours in toluene no appreciable change in the results of the 

 test was found, showing that the toluene did not enter the kernels 

 to any extent. Toluene apparently does not dissolve out any great 

 amount of fats and oils from the kernels, as is evidenced by the fact 

 that, if filtered after using, its specific gravity is found not to have 

 changed materially. Commercial toluol, costing from 35 to 40 cents 

 a pound, can be used instead of the more expensive chemically pure 

 toluol. This commercial product has a specific gravity of about 

 0.8667 and will not change materially if kept in a cool place in a tight 

 can or bottle. 



Alcohol, when tried, exhibited a tendency to soak into the kernels 

 when suction was applied. Alcohol also changes in its specific 

 gravity, thi^ough evaporation of alcohol and the consequent increase 

 in the relative proportion of water, to an extent that renders the 

 results of little value. On the other hand, the results obtained 

 without applying suction when toluene was used were not correct, as 

 was evidenced by the way in which air bubbles were given off when 

 the bottle was connected to the aspirator. 



[Cir. 99] 



