October 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
it seems advisable, therefore, to determine the moisture content of the paper on separate samples. It frequently has been pointed out that the empirical nature of the copper number determination renders it highly dependent on the details of the experimental procedure. The temperature during the digestion period (2, Q, lQ), the time of digestion (9,9), and the concentration of the alkaline solution ( I ) must be kept constant if strictly comparable results are to be obtained, The reproducibility of the results can be illustrated from the following: Ten copper number determinations made on a given cable paper averaged 0.96. The highest value was 0.98 and the lowest 0.95. However, abnormal values, both high and low, are occasionally obtained from the same sheet of cable paper. Whether these are due to actual differences in the paper or to errors in manipulation is not known. Determinations made on a large number of samples of cable paper indicate that it is advisable to interpret the value of a single determination plus or minus about 2.5 per cent.
319
ACKNQWLEDGMENT The authors are greatly indebted to K. S. Wyatt of this organization for his aid in assembling and organizing the data of other investigators and reviewing this work. LITERATURE CITED (1) Barthelemy, Russa, 5, 1111-17 (1930); Pulp & Paper Mag. Can., 30, 421-3 (1930). (2) Braidy, Rev. gQn.mat. color., 25, 35 (1921). (3) Burton and Rasoh, Bur. Standards J . Research, 6,613-19(1931). (4) Clibbens and Geake, J . Teztile Inst., 15,T31 (1924). (5) Gault and Mukerji, Compt. rend., 178, 711-13 (1924). (6) Heyes, J . SOC.Chem. Ind., 47,90-2T (1928). (7) Hirshfeld, Meyer, and Wyatt, Assoc. Edison Ill. Co., Minutes, 625-7 (1930), printed but not published. (8) Jonas, Z.angew. Chem., 41, 960-1 (1928). (9) Koehler and Marqueyrol, MQm.poudres, 8, 73 (1921). (10) Nakano, Cellulose In& 5, 264-9; English abstract, 28 (1929). (11) Okonite Callender Cable Co., private communication. (12) Schoepfle and Connell, IND.ENCI.CHEM.,21,529 (1929). (13) Sohwalbe. Ber.,40,4523(1907); 2. angew. Chem., 23,924 (1910). (14) Staud and Gray, IND.EN+.CHEM.,17, 741 (1925). RECEIVED December 17, 1931.
Impurities in White Sugars VI. Direct Determination of Chlorides J. A. AMBLERAND S. BYALL,Bureau of Chemistry and Soils, Washington, D. C.
c
HLORIDES in sugarhouse products are often determined in the lixiviated ash, although Browne and Gamble (1) have shown that chlorine is lost during the charring preparatory to the lixiviation and recommend the direct gravimetric determination of chlorides in these products. With high concentrations of sucrose and low content of chlorides, however., the sucrose exerts a dispersing action on the precipitated silver chloride, so that collection of the silver chloride upon a filter is very difficult and often impossible. To overcome this difficulty, Budlovsky (2) has proposed a method of coagulating the silver chloride formed in sucrose solutions by precipitating ferric phosphate in the solution containing the suspended silver chloride. The precipitate of silver chloride and ferric phosphate is then treated in a special distilling apparatus with sulfuric acid. The hydrogen chloride liberated is distilled into water and determined by a nephelometric titration with mercuric nitrate. OF CHLORIDES IN PRESENCE TABLEI. DETERMINATION OF SUCROSE
C1- ADDED Mg. 0.35 0.71 1.42 2.13 2.84 3.55 4.26 4.96 5.67 6.38 7.09
C1- FOUND IN C1- FOUND IN PRESENCE OF ABSENCE OF SUCROSE100 GRAMS OF SUCROSE Mg Mg. 0.21 0.21 0.82 0.74 1.42 1.49 2.06 2.20 2.91 2.84 3.62 3.48 4.11 4.33 5.11 5.25 5.75 5.75 6.45 6.31 6.81 7.09
.
The proportion of chlorides present in white consumption sugars is so small that gravimetric determination is impractical. The direct volumetric determination of chlorides in white sugars has not been reported, so far as the authors are aware. The experiments reported in Table I show that Mohr’s method (3) of titration of chlorides with silver nitrate and potassium chromate as indicator may be success-
fully applied. Although sucrose prevents the coagulation of silver chloride, there is no indication that it interferes with the removal of chloride ions by the silver ions. One hundred grams of sugar were dissolved in about 150 cc. of distilled water, and about 0.5 cc. of saturated potassium chromate solution was added. The solution was titrated with 0.02 N silver nitrate solution as usual for the volumetric titration of chlorides. The content of chlorides in various grades of commercial white sugars is shown in Table 11. TABLE11. CHLORIDE ’IN COMMERCIAL WHITE SUGARS SDQAR
c1-
SUQAR
i
i
7.8 1.4 40.4 17.7 33.3 0.7 31.9 14.2 16.3 2.1
c1P. p . m.
P.p . m. k
1 m n 0
P q
r
8
t
33.3 27.7 0.0 6.0 22.7 39.0 44.0 31.9 20.6 10.6
LITERATURE CITED (1) Rrowne and Gamble, Pacts About Sugar, 17,552 (1923). (2) Budlovsky, Z.Zuckerind. cechoslovak. Rep., 52, 421 (1927-28). (3) Mohr, Ann., 97,335 (1856). RECEIVED May 9,1932. Contribution 124,Carbohydrate Division, Bureau of Chemistry and Soils.
CORRECTION. In the article on “Apparatus for Reactions in Liquid Phase at Elevated Temperatures and Pressures” [IND. ENG.CHEM.,Anal. Ed., 4, 342 (1932)], the length of the tubing for the steel spiral referred to in the thirteenth line from the bottom of the first column, page 343, should have been given as 4.3 meters, or 14 feet. HOMER AD KIN^
