254
ANALYTICAL CHEMISTRY
magnvsium by precipitating calcium as the oxalate and titrating the remaining hardness due to magnesium with a salt of ethylenedi:imiiietetraltcetic acid. HARDNESS
I n the review for 1949 it was pointed out that a new method for the direct tit,ration of hardness was rapidly gaining favor, but that very little informat’ionabout the method had been published During 1950 there \vas a landslide movement toward t,he adoption of the direct, method for determining hardness, which \vas accompanied by the appearance of a considerable number of papers in the lit,crature. The method depends on the ability of the sodium salt of ethy-lcnediaminetetraacetic acid to scquest’er calcium and magnesium ions quantitatively. The outstanding features of the direct, colorimetric titration method are speed, precision, accuracy, and simplicity. The soap method a t its best falls far short of the new method in all of these characteristics. The colorimet’ric titration is made by adding a Ftandard solution of the tetraacetate salt to a measured volumct of sample, usually in a 50- or 100-ml. aliquot, in the presence of :I suitable dye, ordinarily eriochrome black T . The color change representing the end point is sharp, distinct, and reproducible. .Among the papers first describing the new method in detail were those b y Betz and Koll (IO),Diehl, Goetx, and Hach (231, a n d Iliehl ( 2 6 ) . Certain ions interfere n-ith the tit.ration, especially iron, copper, and manganese. Directions are given for rrmoviil of the interfering ions or for use of special reagents t o eliminatc interference. Other papers by lfarcy (67, 58), Betz and Sol1 (11), McCrumb (56), Rossum and Villarruz (78))and Willvy arid Senger (99)report favorable laboratory experience with the method. A study by Goet,x, Loomis, and Diehl ( 3 7 ) indicatcs that the st,andard t,etraacetate solutions arc stable to ’ over a period of 4 months. within 1% Jarisen and Spruitt ( 4 7 ) reported further refinements in the Clark (soap) procedure by plotting the time that lather remains unbroken against the volume of soap solution used. The 5minute period is found by interpolation. The authors stated that sodium oleate is preferred t o sodium stearate. COPPER, IRON, ZINC. AND LEAD
The dit.hizone method for determining copper was applied by Swope, Hattman, and Pellkofer ( 8 b ) with appropriate niodification for sewage and industrial \Tastes. Values are read on a spectro- or filter photometer at 510 mp. ‘Accuracy of 0.231 p.p.ni. of copper in 16 replicas of sewage with standard deviation of 0.01‘75 p,p,m. was reported. In another paper, Swope, Jaffe, a n d O’CaIlaghan (87) reported on the determination of metals in industrial wastes using the o-phenanthroline method for iron a n d diethyldithiocarbamate (electrolytic) met’hod for copper. Gad and hfanthey ( 3 2 ) reviewed the thiocyanate method for tot,al iron in Fvater and gave a procedure for a rapid thiocyanatenitric acid-permanganate method. The presence of tannates, humic acids, and ot,her organic compounds in natural waters has frequently led t o difficultmyin the determination of iron. There hasheen considerable evidence that iron is found in organic moleculcbs which do not yield the iron quantitatively in the ordinary procedures of analysis. Bastisse ( 8 ) reported new evidence of complex organic iron molecules in irrigation drainage waters. Zinc has been determined polarographically by De Salas a n d Graclls (21). A sensitivity of 0.5 p.p.m. is reported. The dithizone method for lead was studied by Buczkowska ( 1 4 ) using tartaric or citric acid t o prevent precipitation of ot,her metals. KO interference was observed up to 10 p.p.m. of iron and coppcr, 10 p.p.m. of zinc, and 20 p.p,ni. of manganese. As little as 0.5 p.p.m. of tin produced up to 35% error. The rnet,hod is sensitivc to 0.01 p.p.ni, of lead.
SODIUM AND POTASSIUM
Although the flame phot,ometer appears to have gained ti-ide favor in the determinat,ion of sodium and potassium, very litt,le has been published on this application during the past year. West, Folse, and lfont,gomery ( 9 7 )described the Beckman flame photometer and the use of radiation buffers in the determination of sodium and potassium. The inst,rument was also recommended for calcium. Connors ( 1 9 )mentioned the instrument in a brief paper discussing advances in methods of water analysis. llestayer (5Q)determined sodium by precipitating it, as the Bfter cencomples salt 3U02(0.~c)i.~lg(0.iic)~.SaOhc.8Hz0. trifuging, the precipitate is dissolved in acetic acid, and color is developed with potassium ferrocyanide. Concentrations of lithium and strontium over 0.5 p.p.m. interfere, but potassium up t o 4 grams per liter can be tolerated. Potassium was determined by precipitat,ing as cobaltinitrite, dissolving in concentrated sulfuric acid, and titrating with potassium permanganate. Cesium, rubidium, and ammonium over 0.2 p.p.m. interfere.
pH, ALKALINITY, AND CARBON DIOXIDE
hdditional studies have been made on the calculation of the various forms of alkalinity from the pH and total alkalinity. Fahnrich ( 2 7 ) presented nomographs showing the interrelationships and discussed errors made by authors of earlier papers in arriving a t corrections for high concentrations of dissolved solids. Papp (65) took exception t o formulas published by Tillmans, Kolthoff, Langelier, and others for calculating the p H of soft waters which are in a “lime-carbon dioxide balance.” He stated that the difference between actual and calculated pH values increases as the hardness decreases. The errors are said to be due t o failure t o take into account the calcium bicarbonate in solution. Papp developed formulas for calculating pH for waters of varying degrees of hardness. I n another paper Papp ( 6 4 ) calculated the pH of various concentrations of calcium bicarbonate solutions free from carbonic acid. He found that log 2 k / 2 \?-here k is the chemically bound carbon pH = ’7 076 dioxide content of the solution in milligrams per liter. The determination of pH of industrial waste water is often affected by the nature of the wastes. For leather-tanning wastes Evlanova (26) recommended the glass electrode or colorimetry using isoamyl alcohol for evtraction of the original color. For textile plant wastes the glass electrode was preferred, except that the hydrogen electrode was used for bleaching wastes. For sulfite paper plant wastes the glass electrode or colorimetry was recommended.
+
CHLORIDE
The time-honored silver nitrate ( l l o h r ) procedure for the titration of chlorlde in the presence of potassium chromate indicator is probably the most widely used and most generally satisfactory method for ordinary chloride concentrations in water. For concentrations lower than 10 p.p m., however, most analysts evaporate from 100 to 500 ml to a small volume in order t o obtain accurate results. A method has been developed by Clarke (18) which eliminates concentration of a large sample for waters containing less than 10 p.p.m. It is a modification of the method of Dubsky and Trtilek ( 2 4 ) , in which chloride is titrated with mercuric nitrate in the presence of diphenylcarbazone indicator. Clarke presented both titrimetric and colorimetric procedures. An accuracy of 1 0 . 5 p,p.m. for concentrations up t o 200 p.p.m. chloride is reported. The chlorinity (chloride, bromide, and iodide) of sea water was determined by Buljan ( 1 5 )by the usual silver nitrate method, but using different indicators including potassium chromate, sodium arsenate, and fluorescein. Fluorescein gave accurate results, provided coagulation of silver chloride wm prevented. This can be accomplished by keeping the chloride concentration
V O L U M E 2 3 , NO. 2, F E B R U A R Y 1 9 5 1 betwecw 0.066 and 0.053 S,or by adding 2 ml. of 1% gelatin to 15 ml. of sea water diluted with 30 ml. of distilled water. Potassium chromate gave some error and sodium arsenate even more. The use of protective colloids in the argentometric determination of chloride ion \vas reported by Stalzer (82). Gum arabic, gelatin, dextrin, and agar agar Tvere used with varying results. FLUORIDE
i 2 ( ~ oding i to Ballczo ( 7 j, fluoride is readilj- determined by removal from water b). steam distillatioil with perchloric acid and titration of the distillatta with thorium nitrate to form a lake with alizarin. Results arc reported to be “excellent” down to 0.1 p.1).ni. but suliject to increasing e u o r at lolver mncentra-
tions. 1 dii,cic,t iiwthod \vas reported by Thrun (93) using a n aluminum lake of c,i,iochioinecyaniIie to produce a color change from red to pink to orange. For high fluoi-ide concentrations distillation is rrconimrnci~dprior to color developmrnt. modification of the ferric thiocyanate p r o c d u r e clcveloped bj- Foster (28) was described by Ingols el al. (.$,TI. The p H of the d to 1.9 to 2.0 with perrhloric &(*id. After addim thiocyanate, ferric alum. and zirconium oxychloridta, the color of the sample is c-oniparcd wit,h a blanli containing rqual amounts of reagents. Corrt~ctioriis macle for sulfatr, ivhirh interferes. A phot,ometric study of interferences in the alizarin method for fluoride was made by Taras, Cisco, arid Gar~nell(89). They rrcommmded the use of sodium thiosulfate or ultraviolet irradiation to rorrect for interference due to free chlorine, and hydrogen peroxide to reduce interference due to manganrw. NITRITE AND NITRATE
The pink color formed 11y nitrite with resorcinol is the Ilasis of a method described by Shnchez ( 7 6 , 7 7 ) . Chloiitles, sulfates, carbonatw. and small amounts of nitrates do riot intrrfere. Sitrates (wi be determined by the same method t)y heating the samplr n-ith sulfuric and hydrochloric. acids. I3aillie (6j has given direct,ioiis for the preparation of a standard curve foi, determining nitrite with a spectrophotomrtrr at 525 nip. A photometric study of the phenoltiisulforiic &(,idmrthod for nitrates \vas made by Taras (88). He confirmcd the gcnerally ackno\vldged nctrd for removing chloride if presriit in more than very sniall amounts. Although thew is some indication of loss of nitrate when the cvaporated residue is treated with phenoldisulfonic acid. treating the sample with sulfuric acid prior to evaporation to eliminate the bicarbonatr. resulk? in greater losses. Taras roncluded that samples should be waporatcd without adjustiiig the natural alkalinity. A study of the brucine method, for nitrate \vas made liy Gad, Knrtsch, anti Schlichting (31). They concluded that best results a w olitained when nitratc. (as S,06)is in the range of 4 to 10 mg. per liter. Alekin and Chernovskaya ( 2 ) examined the Sol1 method for nitrates t o dtJtermine best conditions. The importance of size and nitrate content of the samplr and the need for uniform reaction t h e tvere strrssed. A micromethod for nitrates was reported by Leithc ( 5 1 ) using ferroiri indicator and titrating with potassium dicahromate after boiling with fcrrous sulfate, sulfuric arid, sodium chlor,ide. and potassium bicarbonate. PHOSPHATE
Sulfamic acid was added to molybdate reagent hv Grcenberg, IVeinberger, and Sawyer (38) t o control interfrrence of nitrite up to 25 p.p.m. in the colorimetric dtAtrrmination of phosphate. The amount of hexametaphosphate remaining in water after threshold treatment n-a? determined colorimetrically by Young and Golledge (101) b i the moljhdate reaction. Tannins, when
255 present, were removed with decolorizing charcoal. Excess phosphate in boiler water \vas determined by PetatskiI ( 6 7 ) by using cation exchange resins. CHLORINE
Methods for t,he determinat,ion of free chlorine in water were reviewed by Gad and Schlichting ( 3 5 ) . In discussing the interference of iron and manganese in the diniethyl-p-pheriyleriediamine and the o-tolidine colorimetric methods, they pointed out that ( a ) iron can be fixed with basic sodium phosphate, and ( b ) after the chlorine is converted to chloramine the manganese can be removed by the addit,ion of cnalrium cwbonatr. Gad and Priegnitz ( 3 4 ) also dcwrihed a procedure for determining chlorine by use of methyl orange, methyl yellow, or methyl red. Methyl orange appears to give, hest results. Iron is reported not to interfere. A sensitive colorimetric. p~.oc.edurefor determining free chlorine (or bromine) was reported b>- .\lilton (61). I t involves the use of sodium (,!-anide arid pyridine containing a small amount of beiizidene hydrochloride, The reaction produces intensely colored dianil derivatives. A patent was issued to IVallacc (95) for a device which nil1 record high concentrations, or produce audible or visual signals when predetermined ronccntrations of chlorine in water are exceeded. Methods for determining the chlorine hydrolysis products in water were rrportcd h y IIermanowicz and Dozariska
(41). D1 S SO LVED OXYGEN
Although thc \\inklcr method is generally recognized as the best, method for determining dissolved oxygen, many useful modifications are constantly twing worked out. For determining low conrentrations of dissolved oxygen in degassed water, Delassus, Devaus, arid Jlontigny (20) have reviewed esisting mcthotis and h a w rq)ortcd favorably on two methods for oxygen in the range of 0.000 t o 0.072 mg. per liter.. In the upper part of this range the Perlry poteiitiomrtiic method is preferred. I n t,he lo\ver part of the range a colorimetric method utilizing the yellotv color developed tiy o-tolidine with chlorine liberated from the \Vinkler reagmt is said to give reliable results. An ac-curacj. of 2 5 for coricwitrations tielow 0.003 mg. per liter is repomi. A h o t h e r modification of the \Vinkler method for determining dissolved oxygen in deaerated water for concentrations brtween 0.005 and 0.02 ml. per liter was described by .4rnott, .\IcPheat, and Ling ( 4 ) . The liberated iodine is extracted with carbon tetrachloride. Sodium thiosulfate is added in excess and backtitrated with standard iodine solution. >laximum error of 0.002 ml. per liter of oxygm is reported. Dissatisfaction with the Itideal-Ste\vart modification of the \\-inkier method prompted CamcAron ( 1 6 ) to devise a procedure whereby there are added t o a +ounce bottle of sample the following: 0.5 ml. of a 40% solution of manganese sulfate, and 0.5 ml. of a solution containing 3XC; sodium hydroxide, 20Vc potassium iodide, and 0.8%, sodium azide. After 10 minutes, 100 ml. are titrated with 0.0125 S sodiuni thiosulfate. .4 titrimetric method for determining dissolved osygen without the use of iodine-cont,aining reagents was described by Gad (29). I t is a modification of the Leithe procedure using manganese chloride, sodium hydroxide, sodium pyrophosphate, and diphenylamine in sulfuric acid. The final titration is made with 0.01 S ferrous sulfate. The use of various preservatives including xylene, chloroform, and mercuric chloride was studied b>-Alekin and S’oronkov ( 3 ) t o prevent, loss of dissolved oxygen iii samples stored under different conditions. Mercuric chloride was found most effwtive. Storage in an alkaline condition and a t the temperature at Fhich samples are collected is recommended.
256
ANALYTICAL CHEMISTRY
BtOCHEMICAL OXYGEN I>E>I.4NDAND OXYGEN CONSUMED
The B.O.D. test continues to be the subject of intensive study. Although i t is not a precision t.est and is subject to numerous c t ~ o r and s misinterpretations, it. still appears to be the best single n i ~ a n sof determining t,he oxygen-consuming potential of water. One of the difficult,ies in B.O.D. work is agreement in the use of priinary standards. Glucose and glutamic acid have l)een rrc.oniinended by Sawyer et al. ( 7 8 )as suitable standards. A wview of the fundamental background of biological osidation of industrial water was puhlished by Heukelekian (4%). A t (twtion was given to food, seeding organisms, and environinerital factors. Ingols ( 4 4 ) reported on a study of the variation of B.O.D. with time, using the rate of decolorizing of methylene blue ab a possible measure of the reaction. R e concluded that the rate of decolorizing conltl not l x correlated with the B.O.D. of tlir sample. I.;speriences with modifications of the B.O.D. test \\ere reportid b y Mohlman ef al. (62). Efforts were made to suppress nit r i t i d i o n . Pasteurizat,ion ant1 reseeding, as well as acictificatiori xnd neutralization, did not appear t o depress the normal 1LO.I). of raw sewage or ImhotY tank effluents, but did reduce the 13.0.1). of activated sludge apprrciably. Chromium salts reduced the B.O.D. of raw and settled sewage to a very great extent. The depressing effect of chromate ions was also reported by Plawk, Ruchhoft, and Snapp ( 6 8 ) . Copper has a similar effrc*t,but not so pronounced an effect as chromium. The reseeding of B.O.11. bottles :it the end of 24 and 48 hours iu the absence of oxygen was reported by Borden and JVoodcock ( 1 8 ) to eliminate interferrnce by toxic materials. In control tests the reseeding raised the B.O.D. of treated waste to values approximating those obtained t)rt‘ore t.reatnient. The R.O.D.’s of several common organic rompourids were report,ed by St rorig, Shrewsbury, and Hatfield (84). Technique for the B.O.D. determinations a t 50% oxygen dcplction was described by Rogers ( 7 1 ) . Results of a 6-month study of t’he ’Winkler volumetric procedure were published by Imvin ( 5 2 ) . The merits of using 1)iochemical oxygen demand 01’ oxygen consumed to measure the strength of sewage and trade wastes w r r discussed by Ingols, I-iildehrand, and Ridenour ( 4 6 ) . The rrsults obtained from osygcw cwisumed determinations using the acid-dichromate method wt’rr roilsidered preferable. Graphs for tlrtermining the proper dilution in the B.O.D. test wore presc~rirrtlby Wolfe (loo),antl graphs for determining B.O.1). curve ronstants were described by Tliornas ( 9 1 ) . -4 review of the pernianganatc procedure for determining oxygen consumed with particular rrfcrence to inaccuracies was given by Alciaturi ( I ) . Meyer ( 6 0 ) compared values obtained witli Plrissner’s conversion factors and by Fair’s method and pointed out a lack of agreement with actual observations. The U H ~f ~ silver as a cat in the dichromate reflux method was suggested by Muers ( 3lISCE LLAN EOUS
IIiltiger ( 4 9 ) described a method for determining dissolved solitls in water in whirti the sample is passed through ion exchange resin and the liberated acid, equivalent to the adsorbed cations, is neutralized with a standard base. The dissolved aolitls concentration is calculatecl as sodium chloride. hletallic silvrr in water was determined by Gad and S a u m a n n ( 3 3 ) by depositing the silvei, electrolytically and titrating it \vith potassium thiocyanate in the presence of ferric alum. h quantitative colorimetric method for boron was reported by Hatcher and Wilcox ( 4 0 ) . I t is based on the reaction of boron and carmine in concentrated sulfuric acid. It is applicable for all concentrations of boron found in water. The ordinary constituents of water, including nitrites and nitrates, do not interfere. .4lthough scandium is not considered an ordinary constituent
in water, Beck (9) described a niethod involving tlie formation of cubic crystals having the composition [Co(Xi-Ia)e].ScFa. Color was developed with quinalizarin in isobutyl alcohol. Infrared spectrophotometric determination of deuterium oxirk in water was reported by Thornton and Condon (92). An approximate method for the determination of metliane \vxs described by Rossum, Villarruz, and JVade ( 7 4 ) , based oil the equilibrium estnhlished between methane in solution and tlir partial pressure of methane in the vapor above the solution. In order to determine organic carbon in water, Skopintsrv (81) modified the Krogh and Key method. using a roni1)ustion tube attached to a Kjeldahl flask. h spectrochemiral procedure for tlie analysis of brines tvas reported by Russell (7,5) to give results within loc;&. Spertrochemical methods for mineral constituents in w%tc.r \vtlw also described by Jaycox (48). A system of analysis for small quantities of water \vas outlinrd by Gad and Iinetsch (SO) using micromethods. Duggan and hfetler ( 2 6 )devised a field kit for the approsimate chemical anal>,sis of oil field waters. Directions are given for making the kit. The corrosion potential of oil field hrines is determined by analysis of water for unstable constituents such as oxygen, c a h o n dioxide, alkalinity, etc. Watkins (.96) discussed methods applicable for analysis of brines. In a discussion of automatic operations in quantitative analysirc, Patterson and hlellon (66) included several methods used in ivater , for surh determinations as sperific ronductance arid hardness. h method was described by Lyne and AlcI,arhlan (6.5) for determining trichloroethylene in water using pyridine. h u little as 1 p.p.m. could he determined with fair accuracy. Methods for determining trinitrotoluene and hesanit,rodiphenylamine in water and industrial wastes were described by Seifert (80). Riehl and \Vi11 (70) discussed precaution9 to be taken iu the determination of phenols in water and trade wastes using the Scott modification of the Gibbs-Sanchis method. A4dvances in chemical and colorimetric methods iii tvater analysis were described by Connors (18). The paper was primarily concerned with the new procedure for hardness and the flame photometer method for sodium and potassium. .4 review of methods for determining bromine in brines \vas presented hy Haslam and XIoses (3*9). Phenols were selectively extracted from industrial waste waters hy Ricdiger ( 6 9 ) b>-use of mixtures of esters and ethers of t h e higher aliphatic alcohols. Photocolorimetric iodometry was recommeiided by Iiuleriok (49, .TO)for the determination of chlorine and dissolved osygrii. The application of electrical conductivity to water anal! was discussed by Rosenthul ( 7 2 ) and by JVilcox (88). Methods for the determination of chromium, vanadium, antl ryanidr in industrial wastrs \vcrct descrilied t)?, Swope. IIattnian, antl Pellkofer ( 8 6 ) . Studies of clianges in c1iemic:d c*onipositionduring storage \vert’ made by Chernovskaya ( 1 7 ) in which lie used chloroform, s>,lrne, ether, and mercuric chloride as “preservatives.” 4 chromatographic: microprocedure was uwd by Ballczo ( 6 ) for the determination of lithium. Colloidal sulfur in mineral waters was ddtermined by Garc.ia-Fernandez ( 3 6 ) 1 3 ~ -use of an organic solvent and Cetosol. A series of procedures for determining sulfur, boron, arid fluoride in thermal Jvaters \vas published by Schulek and Rcizstl ( 7 9 ) . These procedures are rather involved and probably \voultl not lend themselves to ordinary routine work. The following books will be of interest to water analyst’s: “Examination of Waters and Water Supplies” by Taylor (90); “Tests for Water Used in Steam Generation” (British Standard) (IS); and “Chemische und physikalisch-cheniische Fragen der Wasserversorgung” by Stooff (83).
V O L U M E 2 3 , NO. 2, F E B R U A R Y 1 9 5 1 ACKNOW LEDGTI EhT
The author \Tishes to acknowledge with appreciation the assistance of Sarah B. Koland, who made the literature search. Ackno~vledgmentis also made to the material in Chemical Abstracts, which was the major source of the information given in this revim . LITER4TURE CITED
(1) .Ilciaturi, F. A , d i i o i r s asuc. q u i m . y j ‘ u r m . C-ruguay, 50, 148-55 (1949). (2) .4lekin, 0. A , , and Chernovskaya. E. S . , Voprosy Gidrokhim. (@sudarst. Gidrol. I n s t . ) , 1946, h-0. 32, 74-80. (3) Alekin, 0. -4., and Voronkov, P. P., Ibid., 1946, S o . 32, 98-116. (4) Arnott, J., hIcPheat, J . , and Ling, F. B., Engineering, 169, 553-5 (1950). (5) Baillie, E. P., Sewage T o r k s J . , 21, 840-3 (1949). (6) Ballczo, H., Mikroclienzie w r . Mikrochim. Acta, 35, 178-88 (1950). (7) Ballczo, H., Osterr. Chern.-Ztg., 50, 146-8 (1949). (8) Bastisse, E. M., Compt. rend., 229, 521-2 (1949). (9) Heck, G., Mikrochemie uer. Mikrochim. Acta, 34, 423-5 (1949). (10) I3etz, J. D., and Soll, C. .I.,J . Am. Water W o r k s Assoc., 42, 49-56 (1950). (11) Ibid., pp. 749-54. (12) Rorden, G. C., Jr.,and W7‘qpdcock,I., T a p p i , 32,506-16 (1949). (13) British Standards Inst., British Standards 1427,” London, 1949. (14) Buczkowska, Z., Gaz, V o d a i Tech. Sanit.. 24,99 (1950). (15) Buljan, M., Acta Bdriot., 3, 383-404 (1948-49). I n s t . Sewnge Purif., J . a n d Proc., 1947, Pt. I, (16) Cameron, Vi. M,, 21G12. ~~. (17) Chernovskaya, E. l-., Voprosy Gidrokhiln. (Gosudarst. Gidrol. I n s t . ) . 1946, KO.32, 87-97. (18) Clarke, F. E., ANAL.CHEM.,22, 553-5 (1950). (19) Connors, J. J., J . Am. Wuter W o r k s Assoc., 42, 33-9 (1950). (20) . . Delassus. M..Devaux. R., and Rlontigny. P., Chaleur & Ind., 30, 159-68 (1949). (21) De Salas, S.hI., and Graells, R. 9..Anales asoc. Q u Q ~ Argen. tina, 37, 208-34 (1949). (22) Diehl, H., ASAL. CHEM.,22, 503 (1950). (23) Diehl, H., Goetz, C. A., and Hach. C. C., J . A m . Water W o r k s A S S O C42, . , 40-8 (1950). (24) Dubsky, J. V., and Trtilek, J . , Mikrochemie, 15, 302 (1934). (25) Duggan, hl., and Iletler, A. T,, ANAL.CHEY.,22, 200 (1950). (26) Evlanova, A. V.,Zazodskaya Lab., 15, 1371-2 (1949). (27) FBhnrich, V., Chem. Obzor., 25, 33-6, 49-52, 65-8 (1950). (28) Foster, RI. D.. IXD.ESG. CHEY.,ASAL. ED.,5, 235 (1933). (29) Gad, G., Gesundh.-Ing., 69, 22-3 (1948); Chem. Zentr. (Russian Zone Ed.), 1948, 11, 342. (30) Gad, G., and Knetsch, M., Uesundh.-Ing., 70, 259-61 (1949). (31) Gad, G., Knetsch, h I . , and Schlichting, H., Ihid.. 69, 137-9 (1948); Chem. Zentr. (Russian Zone Ed.), 1948, 11,760. (32) Gad, G., and 3Ianthey. l l . , Gesundh.-Ing.. 71, 27-9 (1950). (33) Gad. G., and Saumann, K., Ibid., 68, 29-31 (1947); C h e n . Zentr., 1947, 11,7 2 . (34) Gad. G., and Priegnitz. E.. Gesundh.-Ing., 68, 174-6 (1947); C h e m Zentr., 1947, 11, 1022. (35) Gad, G., and Schlichting, H., Gesundh.-Ing., 68, 148-51 (1947); C‘hem. Zentr., 1947, 11, 1022. (36) Garcia-Fernandea, E., Bull. sue. chim.France, 1949, 430-3. (37) Goetz, C. A , , Loomis, T. C‘.,and Diehl, H., ANAL.CHEM., 22, 798-9 (1950). (38) Greenberg, -4.E., Weinberger. L. IT,, and Samyer, C. A , Ibid., 22, 499 (1950). (39) Haslam, J., and Moses, G., Analyst, 75,343-52 (1950). (40) Hatcher, J. T . , and Wileox, L. V., .%XAL. CHEM.,22, 567-9 (1950). (41) Hermanowicz, I T . , and Dozanska, IT., Gat., W o d a i Tech. Sanit., 23, 280-5 (1949). (42) Heukelekian. H.. Sewage and I n d . Wastes, 22, 87-93 (1950). (43) Hilfiger. J. P., C h i m . anal., 31, 226-7 (1949). (44) Ingols, R. S., Sezcngr W o r k s J . . 21, 984-91 (1949). (45) Ingols, R. S.. et ( I [ . , . ~ N A L .CHEM.,22, 799-803 (1950). (46) Ingols, R.S..Hildebrand, J. C.. and Ridenour, G. M.,Water & Sewage W o r k s . 97, 21 7 (1950). ~~
257 Janssen, C., and Spruitt, D., Anal. Chim. Acta. 3, 360-9 (1949). Jaycox, E. K., ANAL.CHEY.,22,507 (1950). Kulenok. hf. I., Gigiena isunit., 13, No. 11, 5-9 (1948). Kulenok, 11.I., Z h w . Anal. Khim., 4, 248-54 (1949). (51) Leithe. JY., ik’ikrochemie cer. Mikrochim. Acta, 33, 149 (1947); Chimie & indzistrie, 60, 455 (1948). 1.52) ~-~ Lewin. V. H.. I n s t . Sewaoe Purif.. J . and Proc.. 1949. 140-55. (53) Love, S. K., . ~ N A L . &E
