THE DETERMINATION OF CANE SUGAR 519 



essential change of sucrose to invert sugar which it is the object of the anal- 

 ysis to obtain. The method of Saillard has been developed by Jackson 

 and Gillis, who use ammonia as the neutralizing agent, and take the direct 

 reading in the presence of the appropriate quantity of ammonium chloride. 

 They call particular attention to the necessity of exactitude in the analysis, 

 failing which, errors, other than those intended to be eliminated, may be 

 introduced. A scheme, one of several proposed by them, but quite general, 

 is quoted below, and it may be mentioned that this scheme takes into 

 account the effect upon the rotation of cane sugar of the ammonium chlo- 

 ride used in the direct reading. 



Jackson and Gillis .General Double Neutral Polarization Method. 



20 

 Reagents: Hydrochloric acid d 1-1029 (24-846 Brix) ; ammonium 



4 



hydroxide solution, 5 to 6 N ; solution of ammonium chloride containing 

 226 grams per litre ; pulverized potassium or sodium oxalate. 



Ascertain by at least three concordant titrations in the presence of 

 methyl orange the volume of the ammonia solution required to neutralize 

 10 c.c. of the hydrochloric acid. 



Prepare the normal solution of the substance to be analysed or a solution 

 of such fractional normality as the nature of the material and the sensibility 

 of the saccharimeter will permit. Clarify with the minimum quantity of dry 

 basic lead acetate. Shake thoroughly and filter. 



(If desired, the solution may at this point be freed from lead ; but, if 

 this is done, the de-leading reagent must be added to the whole filtrate. 

 Finely pulverized potassium oxalate in minimum quantity is added until 

 precipitation is complete. Filter. If this procedure is omitted, the lead is 

 precipitated satisfactorily by the chlorides added later). 



Pipette into two 100 c.c. flasks two equal volumes of the filtrate (50 c.c. 

 70 c.c., or 75 c.c.). 



For the direct polarization, add to one portion 15 c.c. of the ammonium 

 chloride solution or 3-392 grams of dry ammonium chloride. Complete to 

 volume at the temperature at which the observations are to be made ; 

 filter, if necessary, and polarize. 



For the invert polarization as follows : Pipette 50 c.c. into a 100 c.c. 



20 

 flask, add 20 c.c. of water and 10 c.c. of hydrochloric acid, d- 1-1029; 



4 



immerse in water bath at 60 C. for 9 min., agitating continually and cool 

 quickly. After the solution has become quite cold, add from a burette 

 while continually shaking the precisely determined volume of ammonia 

 required to neutralize the acid. Adjust the temperature, make to volume, 

 filter, if necessary, and polarize at carefully controlled temperature. 

 Multiply both polarizations by the factor 



Volume of original solution containing 26 grams of sample. 



Volume of solution taken for polarization. 



The algebraic difference between the corrected polarizations gives PP'. 

 If the original filtrate contained 26 grams in 100 c.c., refer to the following 

 table, and under the column which designates the volume taken for the 

 invert polarization find the value of the divisor. Apply the temperature 

 correction and divide into PP'. If the original solution contained a 

 fraction of 26 grams of the sample, multiply P P' by this fraction before 

 referring to the following table. Divide into PP' 



