SACCHARINE PRODUCTS. 



73 



Wooden holder: Cm. 



Length 7. 7 



Diameter 3.2 to 3.5 



Diameter of center hole to fit stem 1.3 



The tube and holder weigh about 50 grams, arid should be so constructed that 

 when fitted together the bottom of the tube will be exactly even with the lower 

 surface of the holder. In a set, each couple, tube and holder, should be made 

 to balance each other. There should be, as nearly as possible, a balanced load 

 carried at the circumference of the wheel of the centrifuge. 



(b) DETERMINATION. 



Introduce into the tube 5 cc of sirup or 5 grams of sugar, add 10 cc of water, 

 and dissolve. Add 0.5 cc (10 drops) of alumina cream (prepared as directed 

 under "VI. General Methods," p. 40) and 

 1.5 cc of lead subacetate and shake thor- 

 oughly. Allow the mixture to stand from 

 forty-five to sixty minutes, occasionally 

 giving the tube a twisting motion to fa- 

 cilitate the settling of the precipitate. Place 

 the tube with its holder in the centrifugal 

 machine and run six minutes under the 

 conditions given below. If any material 

 adheres to the sides of the wider portion, 

 remove it by means of a small wire pro- 

 vided with a loop at the end. Return the 

 tube to the centrifuge and run six min- 

 utes longer at the same rate. Note the 

 volume of the precipitate, estimating to 0.01 

 cc as closely as possible. Run a blank, 

 using water and the reagents named above 

 and correct for same. In the case of a 

 sirup the result is reduced to the 5-gram 

 basis by dividing by the specific gravity 

 of the sample. If the sugar content of the 

 sample is known, the specific gravity is 

 found from Table VI, page 221. 



The centrifuge used in this method has 

 a radius of 18.5 cm and is run at a speed 

 of 1,600 revolutions per minute. The ve- 

 locity at the circumference of the wheel is 

 computed in centimeters per second. Calling M (mass) unity in the formula 



F= , the numerical expression for F, the centrifugal force, becomes 519,363. 



By measuring the radius (r) for any given machine and substituting for F, 

 the numerical constant determined above, the velocity for a given machine may 

 be determined by the following formula, v=\/Fr. Given the velocity in centi- 

 meters per second, the required number of revolutions per second or per minute 

 can be computed. 



\ 







Tube. 



Holder. 



FIG. 1. Apparatus for the determination 

 of lead subacetate precipitate in maple 

 products. 



