INDUSTRIAL A N D ENGINEERING CHEMISTRY
January 15, 1931
iron wire or sodium oxalate is used. The iron solution contains ferrous ammonium sulfate and sulfuric acid in concentrations of 0.1 N and 0.3 N , respectively. The preventative solution contained 67 grams of MnS04.4Hz0, 138 ml. of 85 per cent phosphoric acid, and 130 ml. of sulfuric acid (concd.) diluted to the volume of 1 liter. The comparison of this method with the standard method is given in the determinations, used in Table 11,which utilized various dilutions of waste liquor from sulfite digesters in sea water obtained from Seattle harbor. With this constancy of results it is obvious that the oxygenconsumed values may be used to indicate the concentrations of sulfite liquor when it is known that it is the polluting agent in sea water. By making up the various dilutions and taking the mean of five determinations on each dilution the results used in Table I11 were obtained. Table 111-Oxygen Consumed with Sulfite Liquor as Polluting Agent DILUTION OF LIQUOR IN OXYGEN CONSUMED OXYGEN CONSUMED BY SEA WATER BY MIXTURE DIGESTER LIQUOR Mdliter M ~_. /.l i l e r Blank 11.3 0.0 73.7 1 : 1000 62.4 32.8 21.5 1: 5000 12.4 23.7 1 :7500 18.3 1 : 10,000 7.0 13.7 2.4 1 : 30,000 11.5 0.2 1 : 50,000 11.3 1: 100,000 0.0
When these values are plotted against concentrations the resulting curve (Figure 1) is either identical or nearly so with that obtained by dividing the 5-day biochemical oxygen demand (3’) by the sewage factor 0.68 commonly used to express complete biological oxygen consumption. Inasmuch as Rudolfs (4) has shown that there is a direct relation between the biochemical oxygen demand, bacteria, and plankton, it would seem that the oxygen consumed as determined by this modified method correlates with the other factors ordinarily used for detection of pollution. Abbot (1) has proposed a modified acid dichromate absorp-
31
tion test as a more sensitive index of oxidizable matter than the permanganate absorption test, His values of the percentage oxidation of various organic substances range from 98 per cent in the case of sodium oxalate to 66 per cent for gelatin. To ascertain the degree of completion of oxidation of organic substances somewhat similar to lignin and the other components of digester liquor, the following compounds were submitted to the modified permanganate consumed test: vanillin, tannic acid, starch, sucrose, and pyrogallol. Complete oxidation is defined according to the following reactions : Vanillin: Tannic acid: Starch: Sucrose: Pyrogallol:
++ ++ +
++ + +
CsH& 17 (0)+8COs HzO C14HloOg 24 (O)---t14cO~ ~ H z O C6Hlo05 12 (0)+6C02 5H20 ClzH~~Oll +24 (0)+12C02 1lHzO C6He03 12 (0)+6C01 3Hz0
After making correction for the oxygen consumed by the blank, the results given in Table IV were obtained by the modified method. Table IV-Modified Permanaanate Consumed Tests WEIGHT O F OXYGEN REQUIRED COMPLETE SUBSTANCE SAMPLE Theoretical Actual OXIDATION Gram Gram G7am % Vanillin 0.0159 0.0285 99.0 0 0282 Tannic acid 0.0056 0.0067 65.5 0.0044 Starch 0.0527 0.0626 72.0 0.0451 Sucrose 0.0408 0.0446 0.0372 83.5 Pyrogallol 0.0130 0.0196 77.5 0.0152 I
From the similarity of these substances to those present in digester liquor it would be reasonable to expect that their oxidation is from 85 to 90 per cent complete. Literature Cited (1) Abbot, IND. END. CHEM.,19, 919 (1927). (2) American Public Health Assocn., “Standard Methods for Examination of Water and Sewage,” 6th ed., p. 24, footnote. (3) Benson, Paper Trade J., 90, No. 24, 69 (1930). (4) Rudolfs, IND. END. CHEM.,21, 256 (1929). (5) Treadwell and Hall, “Analytical Chemistry,” Vol. 11, pp. 515-8, footnote 2.
Modified Ford-Williams Method’ L. H. James REOMOTOR Co., LANSING,MICH.
T
HE following procedure is applicable to the determi-
nation of manganese in high chrome-nickel alloys which are practically insoluble in nitric acid. Such alloys are, however, soluble in nitro-hydrochloric acid. If either the persulfate or bismuthate method is used for determining the manganese in nickel-chrome alloys soluble only in nitro-hydrochloric acid, i t is necessary to remove the hydrochloric acid by fuming with sulfuric acid and the chromium with ainc oxide. The only difficulty encountered in this procedure arises from the fact that the complex SUIfates formed often dissolve very slowly after dilution with water. The insolubility of these chromium sulfates probably increases with the temperature and time of fuming, although rather startling variations have been met with in regard to the time required to dissolve the sulfates formed, while working with the same alloy under like conditions. The Ford-Williams method is the O d Y other Practical alternative method used to determine the manganese in such alloys. It is not necessary to separate the chromium in this method, but the hydrochloric acid must be removed by at least two evaporations with nitric acid to a sirupy COnSiStenCy. Received September 3, 1930.
Evaporations of this kind are always somewhat troublesome and time-consuming, The proposed method eliminates the objectionable features of the above-mentioned procedures if the alloy is insoluble in nitric acid, as it is easily carried out, reasonably accurate, and much faster than the methods usually employed. However, if the material to be analyzed is soluble in nitric acid, obviously the following modification cannot be used to any advantage as the Ford-Williams method in its present form has always been recognized as entirely reliable. Method
Weigh 2 grams of sample into a 5 0 0 - ~ tall ~ . form beaker, Add 15 CC. of hydrochloric acid (SP. gr. 1.19), 5 CC. of nitric acid (sp. gr. 1-42), and 20 cc. of water. Boil until dissolved and add 20 cc. of perchloric acid (60 per cent). Continue to boil until the perchloric acid fumes and insoluble salts start to separate. cool, dissolve in 30 CC. of nitric acid (SP. gr. I & ? ) ,and heat just to boiling. Add a few crystals of sodium chlorate in order to avoid excessive foaming and then precipitate with four additions of 2 grams each of sodium chlorate adding each portion after the effervescence produced
Vol. 3, No. 1
ANALYTICAL EDITION
32
by the last addition has about ceased. This precipitation properly carried out should take about 20 minutes during which time the solution should always be saturated with free chloric acid in order to precipitate the manganese completely. If the solution is overheated a t this point, the sodium chlorate decomposes too rapidly and the manganese may not be entirely precipitated. Remove the solution from the hot plate before the effervescence from the last addition of sodium chlorate has entirely ceased, filter on an asbestos pad with suction, and wash thoroughly with water. It is not necessary to allow the solution to cool and settle before filtering although it does no harm. Transfer the pad to the beaker in which the precipitation was made and wash any adhering manganese dioxide from the funnel into the beaker with 100 cc. of water. Dissolve the manganese dioxide in 20 cc. of 0.1 N ferrous sulfate containing 100 cc. of sulfuric acid (sp. gr. 1.84) per liter, and titrate back to a permanent pink end point with 0.1 N potassium permanganate. Calculate the manganese by means of the following formula:
A B C D
[ ( A X B ) - C] X 0.2747 X D Per cent Mn = Weight of sample = cc. of 0.1 N ferrous sulfate = permanganate solution equivalent of the 0.1 N sulfate = cc. of 0.1 N potassium permanganate = normality factor of 0.1 N potassium permanganate
I n order to estimate the accuracy of this method, the manganese in two stainless steels containing approximately 1.5 per cent silicon, 8 per cent chromium, and 22 per cent nickel, was carefully determined by both the persulfate and bismuthate methods, after separating the chromium with
zinc oxide. The average percentage obtained from four determinations on each steel was assumed to be the correct manganese content of these two samples which are designated in the table as 1 and 2. Determination of Manganese in Eight Samples MANGANESE OBTAINED 2 3 4 Av.
SAMPLE
1
2 12c 72 32a 30b 1oc
7a
%
%
%
%
%
0.85 0.49 0.41 0.64 0.25 0.49 1.12 0.42
0.81 0.50 0.39 0.64 0.24 0.48 1.15 0.41
0.81 0.49 0.38
0.83 0.51 0.43 0.62 0.24 0.50 1.13 0.42
0.83 0.50 0.40 0.64 0.25 0.49 1.14 0.42
0.65
0.25 0.48 1.14 0.42
MANGANESE PRESENT
% 0.83 0 61 0.409 0.651 0.244 0.499 1.13 0 446
The manganese in five Bureau of Standards standard steel samples and one iron (7a) was also determined and included in this table in order to compare further the accuracy of the above method with the commonly used procedures. The results on iron (?.) were obtained without separating the silicon or graphitic carbon. Four determinations on each sample were run at the same time without employing any more care or refined apparatus than is ordinarily used to obtain reasonably accurate results in routine steel work. The theoretical titer was used as shown in the preceding formula to calculate the results thus obtained, which were tabulated without rejecting the percentages obviously inaccurate. These values, however, considered as a whole would be closer to the theoretical percentages if multiplied by 1.02 as an empirical factor.
Investigation of Ammonium Acetate Separation of Sulfates of Lead, Barium, and Calcium' Wilfred W. Scott and Samuel M. Alldredge UNIVERSITY OF SOUTHERN CALIFORNIA, LOSANGELES,CALIF.
METHOD commonly given by standard texts upon quantitative chemical analyses for separating lead from barium and calcium depends upon the solubility of lead sulfate and the insolubility of barium and calcium sulfates in ammonium acetate solution. It is the intention of this piece of work to test out that method as regards its completeness of separation.
A
Previous Investigations
In speaking of the precipitation of lead as a sulfate in the determination of lead in ores and metallurgical products, Treadwell and Hall (7) claim that the precipitate of lead sulfate containing silica and barium sulfate (also strontium and sonietimes calcium sulfate) can be purified by redissolving the lead in hot ammonium acetate solution. They suggest that the lead extraction be made with 20 cc. of hot 2 N ammonium acetate. Low ($1 suggests the use of ammonium or sodium acetate solution in dissolving lead sulfate. He would titrate the lead solution with standard ammonium molybdate solution while the calcium remains out of solution. I n the analysis of fluorspar Sisco (6) claims that lead and barium sulfates are separated by the acetate extraction using a 20 per cent solution of ammonium acetate. Scott (5) considers the bariua? sulfate slightly soluble in 1 Received
August 12, 1930.
ammonium acetate and hence a possible contaminant of the extracted lead. The problem has two main parts-namely, (1) is barium extracted with the lead; and (2) is calcium extracted with the lead when ammonium acetate, hot and concentrated, is used upon a precipitated mixture of the sulfates of lead, barium, and calcium? A subdivision of the problem, however, of minor importance was added by the claim of Majdel (3) that the separation of lead from barium in the presence of barium, by precipitating both components with sulfuric acid and dissolving lead sulfate in ammonium acetate, is not possible as the double salt of lead and barium sulfate is formed which is insoluble in ammonium acetate, and, therefore, a part of the lead remains with barium. The error is greater as the ratio of barium to lead increases. I n proportion of Pb:Ba as 1:0.6,9 per cent lead remains in the undissolved barium sulfate; as 1:1,45 per cent; as 1:2, %per cent; as 1:7, 100per cent; and is thereby lost. The separation must be accomplished, therefore, with hydrogen sulfide. The ratio of 1 lead to 100 barium was taken. The precipitated mixture of their sulfates was extracted ten times with boiling 50 per cent ammonium acetate as given below. The filter and its residue then were boiled with 100 cc. of 50 per cent ammonium acetate until spattering commenced. Fifty cubic centimeters more of ammonium acetate were added, the mixture heated to boiling and allowed to settle.
