ANALYTICAL CHEMISTRY
74 (168) Van Kleeck, L., Ibid., 23, 1311 (1951).
(169) Warren, H., Delavault, R., arid Irish, R.. Bull. Geol. S O CAmer., . 62,609 (1951). (170) Webber, L. A , , and Burks. C. E., A s . 4 ~ .CHmi., 24, 1086 (1952). ~ alLd , lnd. (171) ]veils, IT.,&,hrbauph, p,, and D ~ G.,~sewage Wastes, 24,212 (1962). (172) West, T., Metallurgia, 43, 204 (1951). (173) White, C., J . Chem. Edue., 28,369 (1951). (174) White, J. U . , A N A LCHEY., . 24, 394 (1952).
(175) Wickert, K., W e r k s t o f e u. Korrosion, 2, 209 (1951). 1176) Wickert, K., and Ipach, E., T'om Wasser. 18, 318 (1950). (177) Wickert, K., Ipach, E., and Gauler, H., Ibid., 18, 315 (1950). (li8) Wickert, K., and H.,lbid., 18, 303 (1950). (179) Will, E., Sewage a n d l n d . Wastes, 23, 1288 (1951).
(180) Willard, H. H., and Horton, c. -4.) -4h.AL. C H E l f . , 24, 862 (1952). (181) Williams, D., W a t e r and Sewage Wwks. 98, 429 (1961). (182) Wooster, W., and Rakestraw, K.,J . M a r i n e Research, 10, 91 (1951). (183) Zeppelin, H. v . , and Fuchs, J.,-41tgew. Cheni., 64, 223 (1952).
[End of Review Section]
Recent Developments in Quantitative Organic Microanalysis WOLFGANG KIRSTEY Znstitute of Medical Chemistry, University of CTppsala, Uppsala, Sweden In the determination of carbon and hydrogen the use of tapered ground joints and ball and socket ground joints lubricated with silicone grease avoids diffusion errors. The use of external absorbers for nitrogen oxides and especially Belcher and Ingram's manganese dioxide absorber is a decided improvement. Unterzaucher's method opens the way for ultramicrodeterminations. In oxygen determination the reactions in the carbon filling were investigated. The theory of Boudouard and others, t h a t the equilibrium among carbon, carbon monoxide, and carbon dioxide is independent of the packing form of the carbon, does not appear to be correct a t the temperature of 1100" C. -4modified oxygen determination apparatus is described. In Dumas nitrogen determination the combustion method with oxygen was investigated. Copper oxide which has been reduced and reoxidized several times was found to retain nitrogen oxides when oxygen is present. -4 new apparatus is described which uses burning in oxygen and carbon dioxide and high temperature combustion with nickel oxide and hopcalite. In
R
ECENT developments in quantitative organic microanalysis
have been reviewed in their application to the determination of carbon, hydrogen, oxygen, nitrogen, halogens, and sulfur. apparatus now in use in the author's laboratory, though complicated in some instances, is believed to increase the accuracy, speed, and simplicity of the procedures involved. DETERMINATION OF CARBON AND HYDROGEN
Although the ordinary dry combustion methods have generally given reliable results in the determination of carbon, the determination of hydrogen has been a somewhat unreliable procedure. Lindner ( 4 1 ) made a thorough investigation into the causes of errors in the carbon ar.d hydrogen determination and has given exact figures on their sizes. He found that the highest errors were caused by the high diffusion coefficient of water through rubber tubing, and, to a larger extent, by the uptake and release of water by the hygroscopic lead peroxide m-hich is generally used for the removal of the nitrogen oxides. Several authors have tried to avoid the first error by using ground joints (6, 13, 43, 5O), but an entirely Satisfactory solution of the problem could not be found until the silicone greases and reliable hall and socket ground joints became available. I n the author's laboratory lubricated ground joints are used on the absorption tubes ( 3 2 ) . The tubes are provided with only male tapered joints which can easily be cleaned from the lubricant, and ball and socket joint links are placed between the tubes in order to avoid the risk of breakage.
halogen determination by dry combustion heating of the absorption solution to boiling temperature secures quantitative absorption with simple absorption tubes and small volumes of absorbent. The halogenides are titrated with silver nitrate in alcoholic solution. Mercuric halogenide and diphenylcarbazide are used as indicator. In Carius determination of halogens the ends of the bombs are drawn to capillaries. Slight vacuuni is obtained in the bombs after the combustion by using the reaction 2N0 0 2 = 2N02 and cooling. The capillaries are then broken off under alkali, which is drawn into the bombs. This avoids losses and makes it possible to use volumetric determination niethods also for chlorine. A bomb furnace for continuous work is described. The method for determination of sulfur by oxidation and subsequent hydrogenation is very sensitive, and can be used for ultramicro- and trace determinations. Nitrogen and phosphorus do not interfere. Vanadium pentoxide is used to expel the sulfur from inorganic and aahcontaining organic compounds.
+
Much Fork has been done in order to avoid the erroi introduced by the lead superoxide. Lindner and others (41, 44) use copper to remove the nitrogen oxides. As this makes the combustion rather troublesome, it has not been generally used. Liquid scrubbers were introduced by Domhrowski ( I O ) and by Elving and 1IcElroy (12). Other methods ( 7 , g.5) have aljo been described. The method proposed by Elving and XcElroy seems to be frequently used and has been used for a long time with very good results in the present author's laborstol?: Recently Belcher and Ingrnm ( 3 ) proposed the use of manganese dioxide as an external absorber for this purpose. They claim that the absorbent retains nitrogen dioxide but not nitrogen nionoudc. Therefore an excess of oxygen must alxays be present in the apparatus in order to be sure that only nitrogen dioxide is foimed. Fortunately, in the method for carbon and hydrogen determination used by the present author (38)an excess of oxygen is aln-ays present and the method could therefore be tried m
