97
V O L U M E 2 2 , N O . 1, J A N U A R Y 1 9 5 0 0- and p-cresols have been determined gravimetrically by the cresoxyacetic acid method (1).
The alkaline sample of the cresols is treated with chloroacetic acid, precipitating sodium p-cresoxyacetate. This salt is filtered, dissolved in hot water, and acidified with hydrochloric acid to liberate p-cresoxyacetic acid which precipitates upon cooling. The yield is determined by weighing, the purity by determining the melting point. The filtrate from the p-cresoxyacetate precipitation is acidified and extracted with ether, from which o-cresoxyacetic acid is recovered. From the weight and melting point of this acid the yield of pure aeid is calculated, making reference t o mixed melting point curves of the two acids. An accuracy of 1.5to 2% for the oand p-cresols, respectively, is claimed. Caffeine has been determined in coffee by extracting the ground sample with very dilute (eparation and determination of fluorine (110); methods for the determination of fluorine on a macro scale (110), and micro scale (143); microdetermination of iron (34); determination of magnesium nith &hydroxyquinoline ( 4 1 ) ; conductometric determination of mercurous iron (48); micromethod for potassium using cobaltinitrite ( I S ) ; determination of peroxide with permanganate (65); errors in acidimetric titrations resulting from absorption by filter paper (112); errors in hydrolytic titration of lead nitrate ( 6 4 ) ; influence of acid on the oxidimetric determination of antimony (99); determination of carbon dioxide (98); studies on complex ions of aluminum, gallium, and indium ( 7 2 ) ; studies on the reduction of uranium rom-
98
ANALYTICAL CHEMISTRY
pounds (10); and a discussion of the analysis of cadmium and cadmium plating solutions by various methods (127).
use of ruthenium salts as catalyst in the manganometric determination of tellurous acid ( 7 3 ) .
NEW AND NOVEL METHODS
DETERMINATIONS BY ELEMENTS
Among the new and novel methods which have been employed are: titration of free acid in the presence of iron salts by first reducing the iron to Fe (11) in a silver reductor (115); precipitation titration of azides using adsorption indicators and working under an ultraviolet light (62 ); microvolumetric determination of bismuth by precipitation as iodate or chromate, followed by an iodometric determination of excess precipitant (122); phosphate titration of several metals which may not be very applicable because of interferences (71); conductometric microdetermination of carbon in aluminum after oxidizing the methane liberated to carbon dioxide, followed by adsorption in sodium hydroxide (12); titration of cerium ions with permanganate ( 5 3 ) ; cuprous ion by precipitating with thiocyanate which is dissolved in ferric sulfate, the ferrous sulfate liberated being titrated with dichromate ( 1 7 ) ; use of liquid amalgam and a few drops of chromous chloride to reduce iron solutions (31); determination of iodine iodometrically after oxidizing with chlorine water and then reacting the excess chlorine with potassium cyanide (120): titrating ferric chloride solutions with tartrate using calcium chloride to prevent hydrolysis ( 9 4 ) ; using chloramine-T to titrate ferrous iron ( 1 ) ; phototurbidimetric determination of magnesium in dolomite (108); formation of trivalent manganese complexes with subsequent titration with ferrous sulfate for the determination of manganese (146); determination of nitrate by reduction with chromous ion (77); using ether in the titration of sodium citrate with hydrochloric acid (138); and a volumetric method for the determination of silicon which appears to be rapid and to give good results (148).
Acids. Free acids have been determined in the presence of iron salts after reducing the Fe(II1) to Fe(I1) with silver (116); nitric acid in mixed and waste acid by electrometric titration with ferrous ammonium sulfate (131); hydrochloric acid in distilled water by potentiometric titration with barium hydroxide (33). Aluminum. A rapid electrometric method employing titration with sodium fluoride has been used for ore analysis (28). Several papers have appeared on use of 8-hydroxyquinoline in the analysis of bronzp ( 3 8 ) , silica brick (80), silicates (144), and other materials (100). Antimony. The iodine monochloride end point is suitable for titrating antimony with potassium iodate or potassium permanganate. Ceric sulfate is not recommended (59). The effect of acid concentration on the oxidimetric determination of antimony using permanganate has been studied (99). Pentavalent antimony can be reduced completely to trivalent antimony by use of nickel powder (63). Arsenic. The iodometric titration of arsenic can be made in solutions from p H 7 to 11 (81 ). Methods for the separation of tertiary arsines in mixtures have been developed (106). Bismuth. 4 phosphate titration of bismuth has been suggested, but there are many interferences ( 7 1 ) . A volumetric micromethod has been used in which the bismuth is precipitated aa iodate or chromate, followed by iodometric determination of the excess chromate or iodate (122). Boron. Variations of the usual titration employing mannitol are: in ferroboron ( l 1 3 ) ,in metals and alloys ( 7 ) , and for traces of boron (117). Bromine. 4 method for the microdetermination of bromide ions has been described in Iyhich the bromine is converted to bromine chloride by chlorine water, potassium cyanide is added, and the bromine cyanide is then titrated in the usual iodometrir manner (120). In table salt bromine has been determined iodometrically ($2). Cadmium. A discussion of methods used in analyzing cadmium cyanide plating solutions describes various methods for determining cadmium ( 1$7). Carbon Dioxide and Carbon. The usual barium hydroxide adsorption after converting to carbon dioxide is followed by titration with hydrochloric acid ( 9 8 ) and oxalic acid (118). The carbon in aluminum is determined by conductometric titration of the carbon dioxide formed on ignition (16). One method employs potentiometric titration with barium hydroxide (33). Carbon Monoxide. Carbon monoxide has been determined by oxidizing to carbon dioxide, absorbing in standard barium hydroxide, and titrating the excess with oxalic acid (7,5). Calcium. Active calcium oxide in lime has been determined by boiling with sodium carbonate, folloLYed by titration of the excess sodium carbonate and sodium hydroxide with acid (49). There have been several applications of the usual calcium oxalate permanganate titration to the analysis of magnesia ( l a g ) , sinter cake (148), and silicates (144), and for the determination of small amounts of calcium (70). Cerium. The direct determination, both potentiometric and amperometric, has been made of cerium ions with permanganate in the presence of pyrophosphate (53). Chlorine. Determinations of chlorine in the presence of hypochlorite, chloride, and chlorate ions using arsenite have been made ( 7 8 ) , as well as determinations of all the above constituents in mixtures (86).As an economy measure mercuric nitrate has replaced silver nitrate in chloride titrations (129). Chromium. The usual persulfate oxidation followed by titration with ferrous sulfate has been applied to the semimicrodetermination of chromium in ferrous metals (50),steels (54), cast iron (45), and ferrochromium ( 7 4 ) . For the direct determination
APPARATUS
Several different kinds of apparatus have been described for use
in conductometric titrations ( 9 , 67, 91). An apparatus has been described which can be used for automatic potentiometric titration (76). Several pipets and burets have been described, among which are an automatic pipet and buret (135); pipets of high speed and high accuracy (109); a microburet for transferring known volumes of paste materials (3);and a high precision ultramicroburet using a micrometer gage dial (51). Among useful aids are a rotary stirring device for microtitrations (130); an apparatus for the rapid calibration of volumetric flasks (16); and an apparatus which nil1 absorb boron when analyzing metals ( 7 ) . STANDARDS AND REAGENTS
Little has been done in the past year on new reagents. Ferrous propylenediamine sulfate has been recommended as being stable enough for use as a primary standard (93). Evidence has been submitted to show that ammonium hexanitratocerate may be used as a primary standard of oxidimetry (128). A historical discussion of the use of potassium dichromate as a volumetric reagent has been published (21). The use of silver metal in the buret used to dispense ferrous solutions is of interest (116). Photometric means have been used to standardize permanganate solution but appear to be of no special advantage ( 2 ) . I t has been noticed that certain salts, notably copper and molybdenum, cause air oxidation of tetravalent uranium, resulting in errors when titrating with permanganate (IO). Of the various reagents suggested, the following are of interest: methylene blue in the titration of molybdenum (150); a standard solution of dichromate in the determination of nickel (55); standard arsenite for the determination of chromate ion (133); methyl alcoholic solutions in the titration of &hydroxyquinoline with bromate (100); replacing of silver nitrate by mercuric nitrate in the determination of chlorides (159); the use of sodium vanadate in place of potassium dichromate for titrating iron (107); and the
V O L U M E 22, N O . 1, J A N U A R Y 1 9 5 0 of chromate ion, standard arsenite has been used with manganous sulfate as a catalyst and diphenylamine as an indicator (133). Cobalt. The cobalt is precipitated as the arsonate after dissolving in hydrochloric acid and is determined bromometrically; nickel, however, causes some error (10.2). Copper. A semimicro variation has been made in the usual iodometric determination (36). I n place of the usual iodometric determination, sodium bromide has been used to convert cupric ion to bromide complex ion which can be titrated with thiosulfate (39). Copper has been titrated with thiosulfate in the presence of fluoride ion (37). A method employing dichromate, in which the copper is precipitated as cuprous cyanide followed by dissolving in ferric sulfate and subsequent titration of the ferrous sulfate with dichromate, has been reported ( 1 7 ) . Traces of copper have been determined with dithizone titration ( 1 1 7 ) , which also has been employed for copper determinations in steel (132). Cyanide and Cyanate. Cyanide has been determined by the usual silver titrations (79),and cyanate has been determined by a rather involved reaction in which a final titration with sodium hydroxide is employed (106). Fluorine. Although chlorofluoride methods have been used in ores (101), studies (110, 143) show that the Willard and Winter ( 1 4 7 ) method is superior. This method has been applied to the determination of fluorine in beryllium compounds (26) and in zirconium (27). A method has been suggested for the direct determination of fluorine by titrating with standard ceric nitrate solution in the presence of potassium ferricyanide (104). Hydrogen Peroxide. The determination of hydrogen peroxide with permanganate has been compared to the gas measurement method ( 6 5 ) . In the determination of hydrogen peroxide by iodometry, low results are sometimes obtained (47). Iodine. Iodine has been determined iodometrically after oxidizing with chlorine water and binding the excess chloride with potassium cyanide (120). Iron. .4n alkalimetric method has been described in uhich ferric chloride is treated R ith tartrate and titrated mith alkali using calcium chloride to suppress the hydrolysis of the ferric chloride (94). Both zinc amalgam (31) and chromous chloride have been used to reduce ferric ion (32). A standard chloramineT solution has been used to titrate ferrous iron (1). .4n extension of the work on the determination of ferrous salts in the presence of thiocyanate (18) has resulted in methods for the simultaneous determination of ferrous and ferric ions (19) and the determination of iron in minerals and alloys (20). The usual dichromate titration has again been the subject of several papers ( 5 , 23, 141 ). The iodometric titration has been reinvestigated (57)and has been used in a microchemical method for the determination of iron (34) as well as for the analysis of silicates (144). The permanganate method has been used for the rapid determination of titanium and iron by using methylene blue for the titanium end point and 0phenanthroline for the iron end point (125). I n the titration of solutions containing hydrofluoric acid with permanganate better results are obtained if phosphorus acid is added (96). Lead. Small quantities of lead are precipitated as chromate and then determined iodometrically after dissolving the chromate (69). By precipitating with aromatic arsonates, followed by a volumetric titration, lead can be determined in the presence of calcium, barium, or strontium salts (103). In the iodometric titration with sodium phosphate results were shown to vary with the PH ( 6 4 ) Magnesium. A rapid alkalimetric method has been used in carbonate ores in which the sample is dissolved in 0.5 N hydrochloric acid which is then divided and one portion is titrated with eodium hydroxide while the other portion is used for the calcium hydroxide content (114). The use of oxine has been studied (41 ) and used in the analysis of silicates (144). In a rapid method developed for aluminum alloys, magnesium is precipitated with phosphate ions followed by dissolving in acid and titrating with sodium hydroxide ( 5 6 ) . A phototurbidimetric
99 titration has been used for the analysis of dolomites by precipitating magnesium as ammonium phosphate (108). Manganese. A variation of the arsenite titration after oxidizing with persulfate has been employed in the analysis of cast iron (11,84),sinter cakes (64),iron ores (140),and other ores (8). The pyrophosphate complexes have been titrated electrometrically with ferrous sulfate (146). Mercury. A study of the complexes formed during the cyanide titration has resulted in a procedure for mercurous ions using conductometric methods (48). Molybdenum. I n the determination of molybdenum in steel, when the amount is greater than 575, the molybdenum is extracted as a thiocyanate, followed by reduction with zinc amalgam and titration with potassium permanganate (149). In the analysis of ferromolybdenum steel the molybdenum is reduced with zinc amalgam and then titrated with methylene blue; the results are said to be more reproducible than in the usual volumetric method (150). Nickel. The determination of nickel by titrating with dimethylglyoxime is said to be suitable for steels containing up t o 3% copper (55). Nitrogen. For the determination of azides the sample is oxidized with permanganate followed by an iodometric titration (86). ilzides may also be titrated with silver nitrate using adsorption indicators (61). A method for the determination of nitrate by reduction with chromous ion followed by titrating excess chromous ion with ceric sulfate is useful in the 20- to 50-microgram range ( 7 7 ) . Phosphorus. The only thing that has appeared is a variation-of the alkalimetry titration for phosphorus in cast iron (11, 126), phosphate rock ( 6 8 ) ,and basic slag (24). Potassium. A semimicrodetermination of potassium based on precipitation as potassium sodium cobaltinitrite. followed by oxidation Lyith dichromate and subsequent titration of excess dichromate with ferrous sulfate, has been recommended (13). Rhenium. A very interesting discussion on the conditions for the reduction of rhenium to various states should be of assistance in the determination of this element (137). Selenium. A variation of a method employing extraction in chloroform followed by titration with thiosulfate ( 4 0 ) has been used in lead alloys (14). A method which has been stated to be simpler than the American Society for Testing Materials' method consists of precipitating the selenium with hydrogen sulfide, dissolving in nitric acid, and following with an iodometric titration in the presence of urea (134). Silicon. A new and interesting volumetric method for silica which may be of considerable assistance employs precipitation of silicon as quinoline silicomolybdate followed by dissolving in standard sodium hydroxide and then titrating with hydrochloric acid. The method is rapid and the results appear satisfactory (148). Another alkalimetric titration follows the precipitation of silica as potassium silicofluoride (16). Sulfur. A simple procedure for the determination of hydrosulfite consists of titrating with ferric chloride, using a mixture of thiocyanate and ferrocyanide as an indicator (56). In the titration of persulfate, ferrous sulfate has been suggested as a catalyst instead of molybdenum (35). For the sulfate determination there has been a review of microvolumetric methods (136) and an iodometric method for its determination in the presence of calcium ( 9 5 ) . In a variation of the usual procedure for the determination of sulfur in sulfidic ores the roasting gases are collected in peroxide and titrated with sodium hydroxide (119). For the titration of thiocyanate it has been pointed out that when an iodate solution is used, the results obtained are quantitative, whereas they are not if permanganate or ceric sulfate is employed (68). This is in contradiction of a paper (123) which determines thiocyanate by permanganate oxidation in the presence of halogens. Tellurium. Ruthenium has been suggested as a catalyst in the manganometric determination of tellurium (73).
ANALYTICAL CHEMISTRY
100 Thallium. An interesting procedure, which needs some additional investigative work, consists of precipitating thallium iodide using bromophenol blue as an adsorption indicator (83). Tin. I n the analysis of tungsten high-speed steels (124), the tin is precipitated as sulfide, reduced with aluminum, and titrated with potassium iodate ( 4 ) . This titration has also been used for the analysis of copper-based alloys (87). Thorium. By modifying the iodate method of Chernikhov and Uspenskaya (%5) workable procedures have been developed (90, 146). Titanium. For the rapid determination of titanium, titration with permanganate using methylene blue has been suggested (226). Variations in the usual silicate analysis methods have appeared wherein the titanium is titrated with sodium dichromate (I&$). For titanium in ferrous alloys and steels the use of zinc amalgam as a reductor has been suggested (151). Vanadium. A variation in the standard method for the determination of vanadium (62) consists in using the dead-stop titration method for milligram quantities (46). The ferrous sulfate reduction for use in ferrous metals ( 5 0 ) , steel (54), vanadium (66),and chrome steels (SO) has again been published. Water. I n the determination of water the book “Aquametry” gives a literature survey as well as theory and practice (89). A variation of the Karl Fischer method which is stoichiometric may be of interest (121). Zinc. The only addition to the literature on zinc has been a study on the iodometric determination by an empirical method (89). ACKNOWLEDGMENT
The author wishes to express his thanks to F. D. Haisten for assistance with the bibliography. LITERATURE CITED
Afanas’ev, B. N., and Ural’skaya, A. V., Zavodskaya Lab., 15, 407 (1949). Anderson, Sven, Svensk Farm Tid., 52, 339 (1948). Askew, F. A., J . Oil and Colour Chemists’ Assoc., 31, 378 (1948). Bagshawe, B., and Dyke, E., Analyst, 74, 249 (1949). Baron, J., Chim. anal., 31, 29 (1949). Benedetti-Pichler, A. A,, Mikrochemie ver. Mikrochim. Acta, 34, 39 (1948). Bertiaux, L., Chim. anal., 30, 252 (1948). Ibid., 31, 84 (1949). Bever, R. J., Crouthamel, C. E., and Diehl, Harvey, Iowa State Coll. J . Sci., 23, 289 (1949). Bloche, E., GuBron, J., Hering, H., and Provisor, H., Bull. SOC. chim. France, 1948, 1150. Bogdanchenko, A. G., Zavodskaya Lab., 14, 350 (1948). Bolliger, H. R., and Treadwell, W. D., Helv. Chim. Acta, 31, 1247 (1948). Bourdon, Daniel, Chim. anal., 31, 154 (1949). Box, F. W., Analyst, 74, 120 (1949). Budge, E. A., Australian Chem. Inst. J . and Proc., 16, 37 (1949). Budnikov, P. P., and Zhukovskaya, S. S., Zhur. Priklad K h i m . , 21, 959 (1949). Burriel, F., and Conde, F., Anal. Chim. Acta, 2, 230 (1948). Burriel, F., and Conde, F., Anales real soc. espafi. f i s . y quim., 44B, 95 (1948). Ibid., p. 1143. Ibid., p. 1275. Caley, E., and Anders, H. K., J . Chem. Education, 26, 203 (1949). Casini, A., Boll. chim. farm., 87, 207 (1948). Charova, A. M . , and Rutenburg, E. B., Zavodskaya Lab., 14, 872 (1948). Cheritat, Roland, and Vignah, Michel, Chim. anal., 31, 125 (1949) Chernikhov, Yu. A., and TJspenskaya, T. A., Zavodskaya Lab., 9, 276 (1940). Chernikhov, Yu. A , , and Yendel’shtein, E. I., Ibid., 13, 814 (1947). Ibid., p. 815. Chirkov, S.K., Zbid., 14, 783 (1948). Cimerman, Ch., Hebrew Tech. Coll. H a i f a Sci. Pubs., 3, 68 (1948). Claassen, A , , and Corbey, J.. Rec. trov. chim., 67, 6, (1948). I
(31) Cooke, W. D., Hazel, F., and McNabb, W. M., ANAL. CHEM., 21, 643 (1949). (32) Ibj
