ANALYTICAL EDITION
162
two phases, so that in general a change in the index of refraction of the medium can be used to secure information about the index of refraction of the dispersed phase. It was thought that it would be interesting to do this for an absorbing dispersed phase such as carbon black. For this purpose, additional suspensions of carbon black in carbon disulfide and in gasoline cements were prepared. For this range of the index of refraction, 1.489 to 1.617, the extinction depth showed no significant variation. LXTINCTION DEPTHS FOR SUSPENSIONS OF A0 AVP. PARTICLE SIZE .ies p
3aoo
Eg
a00
f
f
;
IO0
G
:: 0
0
.25
.5
X5
1.0
90BY VOLUML FIGURE8
RECIPROCAL OF
OF A0
Figure 6 shows the effect of the index of refraction of the pigment on the extinction depth, giving the curve obtained by plotting the extinction depths for suspensions in xylene cement of barium sulfate, zinc oxide, and titanium oxide against their refractive indices which are respectively 1.64, 2.02, and 2.50. I n Figure 7 we have the calibration curves for the turbidimeter which make possible its use for measuring the average
Vol. 4, No. 2
size of zinc oxide pigments. If there is any question as to which side of the minimum the pigment belongs, it can usually be answered by taking readings with the red and with the blue filters. The ratio of these two readings is different on the two sides of the minimum. LITERATURE CITED (1) Allen, IND. ENG.CREM.,Anal. Ed., 2, 311 (1930). (2) Barnard, J . Roy. Microscop. Soc., 38,1 (1919). ENO.CHEM.,21, 1102 (1929). (3) Bartell and Smith, IND. (4) Bond, Phil. Mag., 7, 163 (1929). (5) Conklin, J . Optical SOC.Am., 10, 573 (1925). (6) Dunn, IND. ENG.CHEM.,Anal. Ed., 2, 59 (1930). (7) Gehman and Ward, Ibid., 3,300 (1931). (8) Green, J . Franklin Inst., 192, 637 (1921). (9) Green, Chem. Met. Eng., 28,53 (1923). (10) Green, J . Ind. Hug., 7, 155 (1925). (11) Green, J. FranklinInst., 204,713(1927). ENG.CHEM.,21, 667 (1929). (12)Grenquist, IND. (13) Hartner, Rubber Chem. Tech., 3,215 (1930). (14) Haslam and Hall, J . Franklin Inst., 209, 777 (1930). (15) Moore, IND.ENG.CREM.,24, 21 (1932). (16) Ostwald, “Licht und Farbe in Kolloiden,” pp. 21,29,Steinkopf, 1924. (17) Parkinson, Trans. Inst. Rubber Ind., 5, 1263 (1929). (18) Siedentopf, veerhundl. deul. phys. Ges., 12, 1 (1907). (19) Siedentopf and Zsigmondy, Drude’s Ann., 10, 1 (1903). (20) Smith, Foote, and Busang, Phys. Rev., 34, 1271 (1929). (21) Spear, Colloid Symposium Monograph, p. 332 (1923). (22) Stutz, J . FrankZinInst., 210,67(1930). ENG.CREM.,19, 61 (1927). (23) Stutz and Pfund, IND. (24) Svedberg, “Colloid Chemistry,” p. 130,Chemical Catalog, 1928. (25) Toerell, Kolloid-Z., 53, 322 (1930). (26) wegelin, Kautschuk, 3, 196 (1927). (27) Wells, Chm. Rep., 3, 331 (1927). (28) Wiegand, India Rubber World, 75, 81 (1926). RQCBIIVED September 10, 1931. Presented before the Division of Rubber Chemistry a t the 82nd Meeting of the American Chemical Society, Buffalo, N. Y . ,Auguat 31 to September 4,1991.
Volumetric Sulfate Determination Rapid Method for Determining Sulfur in Organic Compounds ANDREW CHALMXRS AND GEORGE W. RIGBY,Research Laboratory, Du Pont Rayon Co., Buffalo, N. Y. (2) determination of the inorganic sulfur. Two practicable means of converting organic sulfur into inorganic sulfur are and necessary to follow the course of a reaction by means available: reduction to hydrogen sulfide (6, 19, 21, W), of sulfur determinations. To be of value, these determina- oxidation to sulfate. At present, oxidation by means of tions were of necessity very numerous, and for that reason a sodium peroxide in a Parr sulfur bomb (26) is the most rapid rapid volumetric method has been developed by means of and the most universally applicable method of obtaining the which a complete determination may easily be completed inorganic sulfur. The chief problem, therefore, lies in finding within 30 minutes and as many as six completed within 1 a rapid yet accurate means of determining the sulfate ion in the presence of a large excess of sodium chloride. hour. Determination of the sulfate ion may be based on the Although the principles upon which the method is based are not new, the combination of oxidizing the organic compound insolubility of silver (9), lead (2.6, 26, 38), benzidine (13, 16, in a Parr sulfur bomb followed by a sulfate determination 67, 2& 51), and barium sulfates, the least soluble being barium with standard barium chloride, the excess of which is deter- sulfate. Silver and lead, of course, form insoluble chlorides mined with sodium carbonate solution using phenolphthalein and cannot be used in the present case (58). Benzidine is not as an indicator, may be of value to other organic chemists. applicable in the presence of large quantities of any neutral Three distinct advantages may be claimed for this method over salt, (16). This leaves barium as the best suited for the other proposed volumetric methods: First, a minimum of purpose. Barium chromate ( 1 , 14, 18, 29), phosphate (dW), operations is involved; second, no special reagents or acetate (10, 15), hydroxide (55), and chloride have been used apparatus other than a Parr sulfur bomb are required; and as precipitating agents. The most advantageous appears to third, comparable and quantitative results are obtained in 30 be barium chloride since it forms stable solutions and is available in a very pure state. minutes. Three methods are available for determining sulfate under LITERATURE SURVEY these conditions: (1) photometric (32) determination of The determination of sulfur in organic compounds requires suspended barium sulfate; (2) gravimetric determination (11) at least two steps: (1) conversion to inorganic sulfur, and of barium sulfate; and (3) volumetric determination of excess
D
URING the course of some synthetic organic chemical reactions undertaken by one of the authors, it became
April 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
standard barium chloride used in the precipitation. As rapid methods, the first and third are available. Sodium chromate has been used to determine excess barium chloride (2, 5, 8, 12, 30, 34, 36). This method is undoubtedly accurate, but suffers the disadvantage of requiring an external indicator. Potassium palmitate has been suggested (3, 17, 37, 39), but suffers four disadvantages: (1) the standard reagent is an alcoholic solution; (2) only “purest palmitic acid” can be used; (3) preparation and standardization of the reagent are inconvenient; and (4) a factor must be subtracted from the titration value determined, thus making- the error rather great a t low sulfate concentrations (17). The most promising reaction seemed to be embodied in the work of Vitali (SS), as modified by Cooksey (7) and others (4, 20). The method depends upon precipitating barium sulfate with excess standard barium chloride solution. The excess barium chloride is determined in alcoholic solution by means of standard sodium carbonate using phenolphthalein as an indicator. The advantages of this method do not seem to have been appreciated during the last 24 years, and thus its outstanding advantage as a rapid yet accurate method of estimating sulfates, especially those prepared from organic sulfur compounds, should now be recognized.
PROCEDURE IN SULFUR DETERMINATION Weigh to the nearest milligram 0.5 gram of the organic sulfur compound and transfer to the fusion cup of a Parr sulfur b0mb.I Add 1 gram of potassium perchlorate and 15 grams of sodium peroxide. Seal the bomb and ignite in the usual manner. Cool the bomb under a cold-water tap, remove the cover and transfer the fusion cup to a 400-cc. beaker. Carefully wash any solid adhering to the cap into the beaker by means of a stream of water from a wash bottle. I n this manner add not over 50 cc. of water, then cover the beakerwith a watch glass and tilt by resting one side on a pencil so that the solid is extracted completely from the fusion cup. Solution will be complete by the time another sample has been weighed. Carefully rinse out the fusion cup with water and make the solution slightly acid to phenolphthalein by adding concentrated hydrochloric acid. Cover the beaker with a watch glass, place on a hot plate, and boil for approximately 10 minutes, or until all hydrogen peroxide has been decomposed and all carbon dioxide expelled. Make the solution just neutral to phenolphthalein using 0.2 N sodium hydroxide, and quickly filter through a small Buchner funnel using suction. This step eliminates the iron as hydroxide. A 500-cc. filter flask, moreover, is a convenient vessel in which to carry out the titration. Without cooling, add 100 cc. of No. 30 denatured alcohol (methanol may be used if desired, or 90 per cent grain alcohol, but not No. 5 or 24 denatured alcohol) and 25 cc. of 0.1 N barium chloride. Titrate the excess barium chloride with 0.1 N sodium carbonate to a faint but permanent pink end point. This titration should amount to a t least 5 cc. of 0.1 N sodium carbonate solution. (cc. 0.1 N BaClz
- cc. 0.1 N Na2C03) X 98 = %’ %SO4
OBSERVATIONS Special note has been made that the volume of aqueous solution be maintained a t 50 cc. or less. This is desirable since the end point is almost instantly distinguishable in more concentrated solutions. As may be seen from Table I, this is probably a dilution effect which may be corrected by adding more alcohol, by heating, or both (4). 1 Fok details of operation see book of instructions furnished by the Burgeds-Parr Company, Moline, Ill., observing carefully the modifications
herg presented.
163
TABLEI. EFFECT OF ALCOHOL CONCENTRATION ON ENDPOINT (Commeroial alcohol with denaturant No. 30 used) ALCOHOL ALCO0.1028N 0.0494N ATEND HOL WATER BaCla NaaCOa POINT REMARK5
.
cc.
cc.
cc.
co
10
90
20.00
41.00
20
VOl. % End 6
80
20 * 00
41.50
30
70
20.00
41.55
19
40
60
20.00
41.60
25
50
50
20.00
41.60
31
60
40
20.00
41.70
37
70
30
20.00
41.68
43
80
20
20 * 00
41.65
60
90
10
20 * 00
41.68
56
100
0
20.00
41.70
62
~~
12
point only slightly changed by boiling; very slowly attained (8) Slow end slightly changed by f%kg Slow end point corrected by heating at end point Slow end point completed at room temperature End point readily attained at room temperatmure End point rapidly attained &t room temperature End oaint raoidlv attained at room tempirat-uure End point rapidly attained at room temperature End point rapidly attained at room temperature End Doint rapidly attained at room temperature
Sodium sulfate may be determined quantitatively by this method of titration, as may be seen from Table 11. It would therefore seem possible to standardize the solutions against pure sodium sulfate. It is likewise possible to standardize the carbonate solution against pure potassium acid phthalate in the usual way, the ratio of carbonate to barium chloride solutions being determined in blank experiments. + TABLE11. TITRATION OF SODIUM SULFATE NazSOc 0.1028 N SOLN. ALCOHOL BaClz
cc.
cc.
cc*
25 25 25 25 25 25
100 100 100 100 100 100
40.30 40.35 40.20 100.00 80.00 75.00
0.0494 N NaaCOs
cc.
11.00 10.60 10.40 56.50 15.60 6.50
NazSOd FOUND Grana 0.2574 0.2578 0.2574 0.5310 0.6300 0.5256
NazS04 CALCD. Gram 0.2576 0.2675 0.2575 0.5300 0.5300 0.5300
Sodium chloride seems to have very little if any effect on the end point attained in determining sodium sulfate, as may be seen from Table 111. TABLE111. EFFECT OF SODIUM CHLORIDE ON ESTIMATION OF SULFATE Nak3Oc NaCl ALCO- 0.1028N 0.0494 N SOLN. ADDED HOL BaCL NaaCOa CC. cc. Cc. Grams Cc. 80.60 16.90 25 5 100 25 10 100 80.50 16.80 91.60 40.20 25 15 100
NaaSOd FOUND Gram 0.5286 0.5288 0.5277
Na,SOc CALCD. Grana 0.5300 0.5300 0.5300
It is well to run blanks on the reagents used, especially the sodium peroxide and potassium perchlorate, as these contain appreciable quantities of sulfur unless the best commercial grades are obtained. A convenient manner of running a blank on the reagents is to burn 0.5 gram of pure benzoic acid in the bomb and continue the sulfur determination in the usual way. Ferric iron introduced by corrosion of the fusion cup seems to have no detrimental effect when in the state of basic ferric acetate, other than to mask the end point slightly. Either of two procedures, then, becomes possible at this point. As may be seen from Table IV, the addition of a few crystals of sodium acetate to the hot solution makes direct titration possible without any filtration. On the other hand, by making the solution faintly alkaline to phenolphthalein, the iron is precipitated as ferric hydroxide and may be removed by filtration. Using a small Buchner funnel and suction, the filtering operation is extremely simple and rapid. I n Table V the first value for sulfur in p-toluenesulfonamide was determined after removing iron, and the second without filtering.
164
ANALYTICAL EDITION
EFFECTOF Fe+++ON TITRATION VALUES FeCla RATIO AS 10% ALCO- 0.1028 N 0.0494 N NazCOa. BaCh NazCOa BaCll REMARKS SOLN. AOL cc.
cc.
cc.
cc .
1
70
19.90
47 05
1
70
20.00
41.20
Neutral to henolphthalein with N a 8 H Neutral to phenolphthalein with NaOH 0.2 e. NaOAc 2.092 Neutral to phenolphthalein with NaOH 0.3 g. NaOAc 2.082 Neutral t o phenolphthalein 2 g. Nawith NaOH OAc 2.364 2.060
+ + +
Vol. 4,No. 2
arsenates, borates, and chromates which form insoluble barium salts will seriously interfere with the determination. Likewise, metals which form insoluble carbonates must be removed before the method becomes applicable.
LITERATURE CITED
(1) Andrews, L. W., J.Am. Chem. Soc., 32,476-80 (1904). 1 70 20.00 41.85 (2) Balaohovski, S., 2. anal. Chem., 82, 206 (1930). (3) Blacher, C., Grunberg, P., and Kissa, M., Chem.-Ztg., 37, 56 2 70 20.00 41.65 (19 13). (4) Blaoher, C., and Koerbw, U., Ibid., 29, 722-3 (1905). (5) Briwul, A. A., 2. anorg. allgem. Chem., 156, 210-12 (1926). (6) Caldwell, W. E., and Krauskopf, F. C., J. Am. Chem. Soc., 51, Diluents other than No. 30 denatured alcohol have been 293642 (1929) ; 52, 3655-9 (1930). tried. Acetone, 1-4, dioxane, No. 5 denatured alcohol, pyri(7) Cooksey, T., J . Proc. Roy. Soc., N . 8. W., 41, 216-18 (1907). dine, and No. 24 denatured alcohol were all unsatisfactory, (8) Dominikiewicz, M., Przemysl Chem., 14, 241-5 (1930). whereas methanol, 95 per cent grain alcohol, or No. 30 (9) Frerichs, G., Arch. Pharm., 241, 159-60 (1903). (10) Freud, E., Centr.1, 1, 607 (1892). denatured alcohol proved equally satisfactory. In order that some idea may be gained as to the accuracy (11) Goode, R. E., Refiner Natural Gasoline Mfr., 7, 96-7 (1928). (12) Grigor'ev, P., and Korol, S., J. Chem. Ind. (Moscow), 7, 1004-6 of the results and the applicability of the method, Table V lists (1930). eleven substances which have been analyzed by two different (13) Haase, L. W., 2. angew. Chem., 40,595-9 (1927). analysts. These compounds represent extremes in sulfur (14) Holliger, M., 2. anal. Chem., 49,84-93 (1910). Jander, G., 2. angew. Chem., 42,1037-8 (1929). content as well as in types of compounds which have been (15) (16) Jarvinen, K. K., Ann. Acad. Sci. Fennicae, 2, 22 (1912) ; Centr. successfully analyzed by the method described. I , 1, 526-7 (1912). I. M., and Furman, N. H., "Volumetric Analysis," TABLE V. RESULTB ON SEVERAL TYPESOF SULFURCOMPOUNDS(17) Kolthoff, Wiley, 1929; especially Vol. 11, pp. 180-3. (Obtained by two analysts) (18) Komarowski, A., Chem.-Ztg., 31, 498-9 (1907). SULFUR SULFUR FOUND (19) Kubota, B., and Hanai, S., Bull. Chem. Soc. Japan, 3, 168-72 SUBSTANCE CALCD. Analvst I Analvst I1 (1928). % % " % (20) Litlerscheid, F., and Feist, K., Arch. Pharm., 237, 521-5 (1899). Thiniirea 42.12 42.30 42.28 - .-.. (21) Lorant, I. S., 2. physiol. Chem., 185, 245-66 (1929). 18.72 18.60 18.66 p-Toluenesulf onamide 14.68 14.68 14.55 Diphenylsulfone (22) Macohia, O., L'industria Chemica, 4, 480-3 (1929). 5.74 5.37,5.33 Methyl orange (technical) (23) Meulen, H. T., Opwyrda, H. F., and Ravenswaay, J. H., Chem. Copper sulfate (CuSO4.fiu.n\a Weekblad, 27, 19-20 (1930), 12 83 12.83 12.80 12 72 12 75 "l.r'", 22:43:22:50,22.50 22.56 Sodium sulfate (NazSOd (24) Mindalev, Z., 2. anal. Chem., 75,392-5 (1928). 18.52 Sulfanilic acid (anhydrous) 18.51 18.25 24, 774-8 (1902). (25) Nikaido, Y., J.Am. Chem. SOC., Sodium o-benzoic acid sul(26) Parr, S. W., Ibid., 30, 764 (1908). finide 14 49 14.45 14.52, 14.85 3.65 3.08 QU~ sulfate X~ 3.67 (27) Pezzi, C., Giorn. chim. ind. applicata, 3, 10-11 (1921). 2.97,2.92,2.63 2.36, 2.34 Sulfonated oil (technical) (28) Raschig, F., 2. angew. Chem., 16, 617-19 (1903). l-Arnmo 2-naphthol 413.23 (29) Reuter, M., Chem.-Ztg., 22,357 (1898). sulfonh acid (commkrcial) 13.40 12.97 (30) Roth, H., 2. angew. Chem., 39, 1599 (1926). a Sample dissolved in water, slight excess NaOH added, boiled, filtered to remove copper, and titrated as above. (31) Testoni, G., Ann. chim. applicata, 18, 408-14 (1928). (32) Toepfer, E. W , and Boutwell, P. W., IND.EIQ. CHEW,Anal. In summary it may be said that the method presented offers Ed., 2, 118-21 (1930). five advantages over the other titration methods which have (33) Vitali, D., L'Orosi, 1892, 260-2; Ann., 64, 11, 245 (1892). been tried and which have come to the authors' attention. (34) Wertheim, E., J . Am. Chem. Soc., 52, 1075-8 (1930). (35) White, A. H., Ibid., 24, 457-66 (1902). These advantages are: first, a minimum of operations; (36) Wildenstein, 2. anal. Chem., 1, 323 (1862). second, no special reagents ; third, no special apparatus other (37) Winkler, L. W., Ibid., 53, 409 (1914); 2. angew. Chem., 34, than a Parr sulfur bomb; fourth, positive results obtainable 143 (1921). in less than 30 mihutes; and fifth, apparent applicability to (38) Woodward, G., IND.ENG.CHEM.,Anal. Ed., 1, 117-18 (1929). (39) Zink, J., and Hollandt, F., 2. angew. Chem., 27,437 (1913).
...
.. .
all organic compounds which may be burned in a Parr sulfur bomb. Of course, it should be realized that phosphates,
RECEIVED October 14, 1931.
Thermostatic Control Operated by Ordinary Alternating Current J. B. RAMSEY AND THOMAS A. WATSON,University of California at Los Angeles, Los Angeles, Calif.
A
SIMPLE and effective circuit breaker operated by the commonly available 110-volt alternating current is preferable to any operated by batteries. H. S. Davis (2) has pointed out that the chemist may have overlooked the possibility of operating a relay by alternating current. A few such circuit breakers have recently been put on the market for use in temperature control. L. A. Richards (3) has described an adaptation of a commercial alternating current relay which is operated directly by the 110-volt source. Since the one developed can be made quite readily and since it has proved satisfactory for precise and extended temperature control for the past 3 years, its description may be of value to others.
The assembled circuit breaker is shown in Figure 1. A is an ordinary house-bell transformer, which reduces the 110-volt alternating current t o 6, 12, and 18 volts, respectively. The electromagnet, B C D, is the clapper type, and is activated by a solenoid 1.125 inches (2.86 cm.) in diameter, with a 0.5-inch (1.27-cm.) core, and made of 3325 turns of No. 32 B. &. S. cotton-covered copper wire. Such a solenoid may be obtained from any company carrying standard relay equipment. The armature C is supported at K by two 60-degree pivot bearings. The outer bearing is seated by means of a thumb screw and lock nut to permit the removal of the armature, if necessary, and the adjustment needed for free movement
