THE DETERMINATION OF CANE SUGAR 509 



A fuller decolorization in this process is obtained by the use of sodium 

 hydrosulphite, added just before filtration. The advantage of the process 

 is that nothing is introduced into solution, the products of the reaction, 

 barium sulphate and aluminium h3'droxide, being insoluble. It is not so 

 convenient for use as basic lead acetate, which will continue as the standard 

 defecant, but it may be used for special analj'ses. 



Basic Lead Acetate. — This re-agent, the use of which is due to Clerget,^^ 

 is prepared under a variety of directions : — {a) 130 grams litharge and 430 

 grams neutral acetate of lead are boiled with 1,000 c.c. water, and finally 

 diluted to a densit\' of 1-250. {h) 200 grams litharge, 600 grams neutral 

 acetate of lead and 2,000 c.c. water, allowed to stand for 12 hours with occa- 

 sional agitation. 



Neutral Lead Acetate. — Neutral lead acetate may be used with 

 materials of light colour, but is nearh' useless with substances such as 

 molasses. It may be kept as a solution of 54° Brix. 



Dry Basic Acetate of Lead. — The use of this material is due to Horne.*^ 

 It is used as the anhydrous dry salt and placed directly in the solution. 



Calcium Hypochlorite. — The use of this material is due to Heron^^ and to 

 Zamaron.^" A solution of calcium hypochlorite made by agitating 625 

 grams with 1,000 c.c. of water is filtered and preserved for use in stoppered 

 bottles. It should be of density 1-14 to i-i6. Pellet uses 20 c.c. of this 

 solution in combination with neutral lead acetate to decolorize 4 grams of 

 molasses. 



Basic Lead Nitrate. — This process is due to Herles.^^ Two solutions are 

 used : — [a) 90 grams caustic soda dissolved in 2,000 c.c. of water ; {h) 1,000 

 grams lead nitrate dissolved in 2,000 c.c. water. The lead solution is added 

 to the alkali solution immediateh^ before use, in the proportion of i of lead 

 to i-o or i-i of alkali. 



Mercuric Compounds. — ^lercuric compounds exercise an effect similar 

 to lead salts, but not in so marked a degree. They, however, precipitate 

 amides from solution and are used for the separation of these bodies. The 

 following formula is due to Andersen^^ ; — 220 grams mercuric oxide are 

 dissolved in 100 c.c. of nitric acid of specific gravity 1-39. This is made up 

 to 1,000 c.c. with the addition of 60 c.c. of a 5 per cent, solution of caustic 

 soda. After addition to a sugar solution neutralization is necessary. It is 

 stated that an excess has no effect on the opticity of sugars. 



Animal Charcoal. — By the use of this body, all cane sugar products can 

 be obtained as a brilliant and largely decolorized filtrate. Since sugar is 

 absorbed, as was first shown by Clerget,^^ this material has only a limited 

 and specialized use in analysis. Certain highh* purified charcoals have been 

 prepared in which the absorption is a minimum, but results obtained are not 

 reliable, and the products offered by different dealers vary very considerably. 

 To nuUify the absorption, it has been proposed to saturate the charcoal with 

 sugar before use, but with dilute solutions sugar might then be dissolved 

 out from the charcoal. 



In a second procedure, the sugar solution is filtered through a column of 

 the charcoal and the runnings rejected until absorption no longer takes place. 



A third process aims at obtaining a correction by observing the absorption 

 from solutions of known polarization, and conducting the test under condi- 

 tions exactly equal to those of the check. 



