WATER ANALYSIS S. K. LOVE A ~ DL. L. THATCHER C. S. Geological Suruey, F’ushington, D. C .
T
HIS is the fourth annual review of analytical procedures ap-
Love ( 7 1 ) has presented a review of analytical instruments used in water plant laboratorirs. A continuous odor monitor and threshold tester was developed by Gerstein (31). The sample is fed continuously through a rotameter flowmetcr, heated to 140” F., and sprayed into a bell jar where the operator determines odor using a standard glass osmoscopic nosepiece. Kline (50) describes an automatic sampler for certain industrial wastes. Compressed air is used to operate the apparatus, which takes samples a t IO-minute intervals, and composites them for 24 hourly samples by mrans of a turntable distributor.
plied t o the analysis of water and reported in the technical literature. Previous review were published in 1949 (68))1950 (69), and 1951 (70). I n each annual survey mention has been made of outstanding developments and increasing use of instruments in Tvater analysis. In this review a separate section is devoted to instrumentation. Another section is given over t o the qualitative detection of trace elements in x i t e r , and a third discusses advances in colorimetry applicable t o water analysis. Of great usefulness t o analytical chemistry the world over will be the book “Reagent Chemicals” (18) published in 1950 by the AMERICAN CHF:UIC.IL SOCIETY. This book, which is the culmination of a tremendous amount of work covering nearly half a century, lists recommended limits of impurities and methods of testing for 177 reagent chemicals. S o up-to-datp analytical laboratory can afford to be without it.
TRACE ELEMENTS
The water chemist is often called upon to provide information about trace elements in water. T o make expensive quantitative determinations of a large number of elements that are seldom present in determinable concentrations n-ould require more time and effort than ordinarily can lie justified. Frequently chromatographic or spot tests can he made to indicate the presence or absence of specific trace elements. Quantitative tests can thus be reserved for those elements shown to be present in significant amounts. h paper by Letlerer (66) which gives reference to earlier publications essential to the use of his methods, covers the paper chromatographic identification of a large number of t! ace elements. The chromatograms are developed n-ith hydrogen sulfide, ammoniacal alizarin, azoresorcinol, ferrocyanide, dipicrylamine, hydrogen peroxide, and ammonium rhodizonate. Many of the teste are of sufficient sensitivity for use with natural waters and hariuni, for without concentration, hut Fornr-strontium example--nould require cwnwiitrated samples for sufficient sensitivity. Another complete study of metallic ion identification by mrans of paper chromatography is given by Pollard, RIcOrmie, and Elbeih (98). In addition to most of the metallic ions, a scheme is given for anion analysis including the common anions and many trace anions such as arsenate and chromate. Lacourt and coworkers (59) give a chromatographic scheme which :Is concerned essentially with the more common elements. Oedekerken in two papers (90, 91) preaents a semimicro and spot test qualitative scheme based on the use of specific organic reagents for the identification of the more common anions and cations. Most of the tests are sufficiently sensitive for n-ater analysis and employ accepted reagents-for example, dimethylglyoxime for nickel, Titan yellow for magnesium, etc. Hovorka and DiviS (48)report spot tests for mercury (red), copper (brown )>and cobalt (green) using 2-isotoxime. Prodinger and Kral (105) studied three \veil-known tests, the detection of manganese Tvith Arnold’s reagent, the detection of copper with benzidine and iodide, and the detection of cobalt with pyridine and thiocyanate. S e n and very sensitive reagents for halides a,rereported by Kuznetsov ( 4 7 ) . Silver ion forms a pink complex with 4-(8-hydroxy-5-quinylazo)-benzenesulfonicacid which turns yellow in the presence of agents that precipitate or complex silver (halides, thiocyanate, sulfide, thiosulfate, nitrilotriacetate). The reagent is sensitive to 1 microgram of bromide or 0.5 microgram of iodide. Three other dyes which may be used in the form of the silSer or mercury complexes are described and chloride, bromide, and iodide sensitivities are given. A general review of spot test analysis is presented by FeigI and West ( $ 6 ) .
IY STRURIENTATIOS
Several papers on the general aspects of flame photometry have appeared in the literature. Dunker and Passon ( 2 3 ) discuss the requirements of an instrument for best accuracy. They recommend high gas pressure and a very fine spray. rin important point, sometimes overlooked, is the necessity for identical physical properties (surface tension, viscosity, temperature, etc.) in the sample and standard. Their discussion of effects of stray radiation is more pertinent to instruments using filters to isolate the wave-length spectrum than to the flame spectrophotometers now generally in use. Heidel and Fassel(41) describe a n internal standard flame photometer built around a Gaertner constantdeviation monochromator. Two photomultiplier tubes w e used in a balanced bridge circuit. The instrument features a unique “recycling” atomizer which provides that only the fine spray droplets enter the burner and provides recovery of the condensate of large drops, which usually runs to waste, and recycles this condensate t,hrough the atomizer. Folloxing the trend toward internal standard instruments, Fox (29) describes a filter-type instrument using two barrier-layer cells in a balanced bridge circuit. He uses a centrifugal principle t o provide a fine, dry aerosol which is fed to a >leker-type burner. Excellent reproducibility is claimed using propane or city gas. The inst,rument n’as used for the determination of sodium and potassium and is probably limited to these elements because of the lack of electronic amplification. The subject of operation of flame photometers for best performance was thoroughly discussed a t a round-table meeting of the Division of h a l y t i c a l Chemistry of the ERICA AS CHEMICAL SOCIETY. A digest of the discussion with K. G. Schrenk (114) as moderator outlined the essentially practical aspects of analysis by flame photometry. Rayner and Logie (107) describe a n apparatus that determines the solids in steam condensate automatically. Large samples of water are evaporated in a platinum pan attached to one arm of a balance. The other arm carries a count,erpoise weight and frictionless mercury contact which operates electrical circuits to control the amount of sample delivered t o the pan. A portable meter for determining dissolved oxygen is discussed by March (76‘). Automatic equipment for recording residual chlorine in water is described by Hazey (38). Antimony electrodes are used in a modified cont,inuous recording p H meter described by Kordatzki (53). 294
. V O L U M E 24, NO. 2, F E B R U A R Y 1 9 5 2
295
.AI’€’LlCATlOlvS O F COLORIhlETRY
.Iseries of papers b?- Hiskey, Toung, and Rabinowitz (43, 44) outlines the principles of high precision colorinietry and the application to analytical problems. Comparison of a sample against a standard a t high absorbance values permits accuracy equal to the best gravimetric determinations if the absorhance difference between saniplr a n d s t a n d a d is niade sufficiently small. Very carrful attention to deviations from the absorption Ian- must be observed, hov-evcr. The principles are demonstrated in the determinations of manganese as permanganate (1.94). It is seldoin necessary to make use of the full accuracy of which the method at prment, but in vien. of the rapid is capatile in water anal? adoption of colorimetric methods and their rapid refinement, it may he :inticipated that t h e r \rill some time receive general use a t the higher concentrations IIOK reserved for volumetric and grnvinietric methods. 111such rases it will hr necessxy to make nieasureiiieiit s with all po9sil)le pi‘ecision. Herger and 1-erliestel (6)give a general discussion of colorimetric methods in water analysis, including the fundamentals of light nbsorption and the performance characteristics of several types of photelectric instruments. .I complete outline for the colorimetric determination of trace niet:rls in scvage and industrid n-astcs using the Becknian DL spectro1~hotornetc.ris given by Butts, Gahler, and Mellon ( f j ) , Jvho reconinieiid the following determinations with the reagents :it the wave lengths indicated.
w Cadini II 111 Chronii uin Copper Iron Lraii Manganese ZillC
Dithizon? Diilhenylcarbazide Dirthylhydroxydithiocarbainate 2,2’-Biquinoline 1. IO-Phenanthroline Dithizone Permanganate nithiion?
510 540 435 545 50 8
520 445 235
The universal coniplcsing iiction of ethg1enediamiIietetr:incet;r mid and its salts :IS described in the publications of Srlin.tii,zenh c h and coworkers is estcintling the use of the coinplesiiig agents beyond thc field of c:tlciuni :rnd niagnesiuni titration, where their place has IJeen firmly estakJhhcd. PIihil and coworkers, in a series of pulilications (101-104) are reporting on thr use of ethylenedi:imiiiet~t~~a:rcetic arid salts in metallic ion :inalysis as both roniplexirig agent and colorimetric agent. Thr problem of coniplesing the fluoride ion which interfere? i n several colorimetric dcterniin:ttions made in natuml water \vas att:icked by Feigl :tiid Srh:trffrr (%), ivho u . d berylliuni nitrate a s dein:isking agent for fluoride. The rsti,ccniel>- st:~hIr l i o i v r r tctr:ifluoi,ide onion is formed. IRON, ALUMINUR.1, AND BERYLLIUM
A significant study of iron determinations was reported by Reitz, O’Brien, and Davis ( l o g ) , who studied the effects of variaIiles in three colorimetric iron methods, the 1,lO-phenanthroline method, the thiocyanate method, and the sulfide method, by means of a factorially designed esperinient. This method permits the statistical study of the effect of interactions of several variables as ne11 as the rffect of variation of a single condition. The 1,lO-phenanthroline method was found superior on all counts. The study is of intcrest not so much for its information about three already thoroughly studied iron determinations as for its example of experimental design. Such a factorial design rvould seem to have many possibilities for the laboratory that deals v i t h a wide range of natural n-ater types and niust take account of many variables in the design of its methods. Wells (181) describes a potentiometric titration of iron in low concentration, Lvhich may be of value when better accuracy is desired than is afforded by the colorimetric methods. Haniset and coworkers ( 3 7 ) report on t,he determination of iron with pyrocatechol. An adaptation of the “ferron” iron determination to the Lange colorimeter is described by Haniset ( 3 6 ) . TIYOpapers report on the color-intensifying effect of calcium in
the alizarin red S determination of aluminum. Parke and Goddard (95)take advantage of the effect in a procedure for low aluminum concentrations. Back and Raggio ( 2 ) report similar findings, but also point out that calcium enhances the interferences of iron in the alizarin determination. Kul’berg and Rlustafin ( 5 5 ) studied a series of hydroxy derivatives of anthraquinones as aluminum reagents. They appear to be highly specific and extremely sensitive. They serve as both colorimetric and fiuorometric reagents, with genera!ly better sensitivity in the latter rapacity.. .I typical nieniber of the group is l,-l-dihydroxy-5, 8-dichloroanthraquiiione, which gives a pink color and a yellowgreen fluorescence with aluniinuni. Limits of detection are 0.5 microgram colorimetrically a n d 0.1 microgram by fluorescence. Rolfe, Russell, and Wilkinson (110)report on a study of Chenery’s method of determination with ammonium aurin tricartiosylate using thioglycolic acid as iron reducing and coniplexing agent. The method is sensitive. t o 0.3 microgram. Teicher and Gordon ( 1 2 6 ) describe a separation of iron and aluminum using anion exchange resin saturated n.ith ainnionium thiocyanate. Iron is ahsorbed on the column as t h r negative1.v charged thiocyanate comples. hluniinum is wished out rvith ammonium thiocyanate :it p H 1.0. .It higher pH values rerovery of aluminuni is incomplete. Good separation requires careful control of conditions. Furuhata ( 3 0 ) reports a ne\\- colorimetric reagent for beryllium. Details of procedure are given for colorimetric determination with disodium 3-(5-chloro-2-hydrox~phenylazo)--l,5-dihydroxy2,7-naphthalenedisulfonicacid. There is no fading with this dye as with quinalizarin. The author also recommends turmeric as a qualitative spot teet for beryllium. I n presence of osalic acid the development of the characteristic red color suffers little interference from metals. COPPER AND ZISC
Sedivec and Vakik (117) studied the use of ethylenediaminetetraacetic acid in eliminating the interference encountered in the determination of copper with diethyldithiocarbamate. Interfereiice of iron, cobalt, nickel, arid manganese is completely eliniinated. Silver and bismuth give the customary yellow color, hut these metals are rarely encountered in uater analysis. LaCoste, Earing, and Wiherley (.%) studied the extraction of diethylthiocarbaniates and concluded estraction was an unsatisfactory nicthod of removing interfcrencrs. Haste, Heeremans, and Gillis ( 4 6 ) studied the determination of copper with 2,2’-biquinoline (cuproine) and reported :L sensitivity of 0.02 microgram. Estraction is_necessarg. OkiE and Celechovskq (92)studied the determination of copper with six organic reagents, antipj-rine and potassium thiocymiate, phenolphthalein, benzidine, and potassium bromide, 1,2-dianiinoanthraquinone-3-~ulforiic acid, diphenycarbohydrazidr) and 2 nitroso-l -naphthol-4-sulfonic acid. Interferences are discussed. Polster (99) describes :I spot test adaptation of the Baudisch-Rothschild test using o-nitrosophenol. Sickel, cobalt, hisniuth, and iron give small positive interference. The reagent must be prepared n i t h care. Det:tiled instructions are given. Belcher, Kutten, and Stephen ( 5 ) describe a new spot test for zinc using potassium ferricyanide and naphthidine hydrochloride or 3,3’-diniethylnaphthidine hydrochloride. The latter reagent has a hundredfold :idvantage in sensitivity. Some osidizing agents interfere. Rertiaus ( 7 ) gives a nephelometric determination of zinc based on the precipitation with osine in solution huffered with carbonate. Conditions niust be standardized and ssmple should contain only zinc, ammonium ions, and alkaline earths. Morita (83) reports on a survey of copper and zinc content of sea water near Japan. An improved dithizone procedure was used. CALCILhl, MAGNESILihI. .ARD STRONTIUM
The titration of hardness n.ith sodium salts of the complesones, introduced by Schn-arzenhach, has been almost esclusively per-
296
ANALYTICAL CHEMISTRY
formed using calcium and magnesium indicators for the detection o f i t h e end point, though it is pointed out by Schwarzenbarh that considerable change in p H takes place in the end-point region. Hahn (35) has made use of this principle in the titration of calcium and magnesium with a mixture of ternary and quaternary salts of ethylenedianiinetetraacetic acid, using p H indicators and potentionietric measurements for the detection of the end point. With indicators the titration is accurate to 0.5 mg. of calcium carbonate and with potentiometric measurenient, i t is accurate to 0.1 mg. Ostertag and Rinck ( 9 4 )report the colorimetric determination of calcium n i t h murexide. Nagnesium reduces the sensitivity of the color up to a magnesium to calcium ratio of 40, a t which point the effect levels ~ f f . LePeintre ( 6 7 )reports a modification of the chloroanilic acid method of Gammon and Forbes. Ok&E and Pech ( 9 3 ) report the use of pyrogallolcarboxylic acid as a colorimetric reagent for the alkaline earths, and Pech (96) describes a detailed procedure for the quantitative estimation of calcium. The sensitivity reported is satisfactory for determination of calcium in most natural ll-aters. Lur’e and Sikolaeva (7‘8)report a determination of calcium based on precipitation as calcium potassium nickel nitrite with subsequent colorimetric determination of t,he nitrite or nickel. The determination appears too complicated and susceptible to error for competition with the well-established Schviarzenbach method and its modifications. Rozenberg ( 1 1 1 ) investigated the precipitation of calcium in natural xaters by Bacterium precipitaturn. His finding that up t o 17% of the calcium in concentrations as high as 250 p.p.m. can be precipitated by the bacteria emphasizes a point t h a t has received little consideration in studies of the preservation of natural water samples. The presence of carbon dioxide reduces the effect of the bacteria. Shashkin (118) describes a new colorimetric reagent for magnesium, 1-amino-2-naphthol-6-sulfonic acid. The sensitivity is 1 part in 40,000. Copper, manganese, and high concentrations of iron interfere. Sniales ( 1 2 2 ) reports on a combined flame photometric and radiometric study of the determination of strontium in sea n-ater. The extent of strontium coprecipitation in barium sulfate precipitates was determined by adding strontium 89 to the sample and determining the activity of the barium sulfate brought down. Xnother method involved determination of the original strontium concentration of the sample by flame photometry, and then after precipitation of barium eulfate, addition of standard strontium solution in known amount to restore the original level of strontium radiation intensity. Both methods gave similar results. In six samples of sea water 9 to 11p.p.m. of strontium were found, Previously accepted values were 13 to 13.5 p.p.m. SODIUM, POTASSIUM, AND LITHIUM
Although most water laboratories t h a t make a practice of determining alkali metals now use the flame photometer, results of research on the conventional methods will be of interest to laboratories not so equipped. Belcher and Nutten ( 4 ) describe a n alkalimetric determination of sodium as the triple acetate. Potentiometric titration of the triple acetate and indicator titration are described. Using a mixed indicator, phenolphthalein and bromothymol blue, a range of 1 to 8 mg. of sodium can be covered. With potentiometric t,itration the range can be extended to 20 mg. and the accuracy is improved. The cobaltinitrite determination of potassium has received considerable study with apparently no conclusive results. Belcher and h’utten (3) report inability t o obtain good results with Wilcox’s method involving precipit’ation with solution of trisodium cobalt,initrite, and prefer the reagent prepared with separat.e solutions of cobaltous acetate and sodium nitrite. Studies with x-ray show more uniform composition of precipitate with
the latter reagent. Mason (?a), on the other hand, prefers precipitation with a suspension of trisodium cobaltinitrite in ethyl alcohol. Bourdon (10) reports the cobaltinitrite precipitate to be lower than theoretical in potassium and higher in sodium. The author states 3% as average variation in results. Kriventsov (64) presents a review of the cobaltinitrite method n-ith 108 references. H e claims 0.5 to 0.8% accuracy for a proposed method a t potassium levels above 5 mg. Shawarbi (119) describes a colorimetric dipicrylamine method applicable to a range of 10 to 400 micrograms of potassium. Either fading in color of reagent or color of an acetone solution of the precipitate may be measured. Lithium was studied by Gruttner (SS), who compared the phosphate, sulfate, aluminate, and zinc triple acetate precipitations. The acetate reagent is recommended. Xot more than 2.3 mg. of lithium should be present in the aliquot taken for analysis. The separation of sodium and lithium by extraction of mixed chloride with amyl alcohol is excellent. Wilberg (152) presents a flame photometric procedure for lithium covering the range 0.04 to 0.20 milliequivalent. Potassium gives a positive interference. The necessary correction is easily determined with standard solutions. SULFATE AND CHLORIDE
RIunger, liippler, and Ingols (86) present a determination of sulfate involving the titration of excess barium with ethylenediaminetetraacetic acid after the precipitation of barium sulfate. As the dye, Eriochrome Black, does not function as a barium indicator, it is necessary to add standard magnesium a t the end of the titration (magnesium is also added to the titrant to provide sufficient concentration for obtaining a preliminary end point) and the titration is carried on to the second magnesium end point, which is sharper than the first. Correction is made for added magnesium and the total hardness of the sample. Quevedo (106) describes the conductometric titration of sulfate in water. Calibration curves are prepared with solutions having nearly the same initial conductivity as the unknoan. Concentrated nateis are diluted to a ITorking range of 200 to 800 niicromhos. IIonda (46) describes nephelometric determinations of sulfate n i t h gelatin as suspending agent and the use of ion exchange to remove sulfate impurities in the gelatin, RlcConnell and Jngols (74) give detailed instiuctions for the determination of sulfate with benzidine hydrochloiide. Kol thoff and Kuroda present a potentiometric titration with silver nitrate (51) and an amperometric titration (62) suitable for the very low concentrations of chloride found in natural u-aters. The potentiometric procedure which is applicable down to 0.4 p.p,m, has the advantage in simplicity and suitability for routine use. The titration is made directly to the apparent equivalence potential. A supporting electrolj te of sodium nitrate and nitric acid is used. The amperometric method employs the rotating platinum electrode and gelatin for the supression of maxima, and doee not require the removal of oxygen from solution. Sakaguchi (112) studied the use of adsorption indicators for the argentometric titration of halides. He recommends tetrabromophenolphthalein ester for the chloride and iodide titrations and states that it can he used with 0.0025 S chloride solutions. Cyanosin is recommended for bromide, Clarke (17) in an addendum to a previous description of the chloride titration d t h mercuric nitrate describes the preparation of the reagent and the effect of p H on the titration. FLUORIDE
An interesting determination of the fluorine content of monofluorinated organic compounds found in water is presented by Salsbury et al. (113). The method is applicable t o studies of fluoride “take up” by organic pollutants in connection with fluoridation programs for control of dental caries. Pure fluorinated
297
V O L U M E 2 4 , NO, 2, F E B R U A R Y 1 9 5 2 organics were used as reference compounds in the determinations which involved decomposition with a mixture of pot,assium metaperiodate, silver perchlorate, and perchloric acid, and distillation of the liberated fluorine as silicon tet,rafluoride, followed by titration with thorium nitrat,e using Solochrome Brilliant Blue BS as indicator. X t . h a 20-nil. sample, fluoride as low as 2 p,p.m. can be determined. There is no interference from ions commonly found in n-ater. Aluminum shows no “holding” effect in the dist,illation. B colorimetric procedure is also given. A modificat,ion of the Sanchis fluoride determination is proposed by Boonstra (9). Raising the ratio of alizarin to zirconium to 6 increases the sensitivity sixfold and reduces phosphat’e interference t o a negligible quantity. T h e color is measured a t 530 mp on the spectrophotometer. Taras (Idn‘) discusses the elimination of interference by di Polved chloi~iiir,aluminum, and manganese dioxide in the Sanchie method. X pul)lication l ~ yBuseh, Carter, and McKennn (13) of the Sational Suclear Energy Service describes a critical and coniprelimPive gtudy of nvailtlLle fluoride det~ermiii:itions. Xltliough most of the methods are applicable i o high fluoride concentrntionc, some are sufficiently sensitive for the vei’y low concentr:!tions encountered in water.
and chloramines over the Palin method of titration with ferrous ammonium sulfate. Good results were obtained by Palin’s met.hod in the free chlorine titration, b u t titration of chloramines required low temperat,ure and t h e end point faded rapidly. Reaction of free iodine with the o-tolidine indicator was the SUPpected cause of fading. I n contrast, t h e amperometric titration (authors propose phenylarsenoxide in place of the cust,oniary arsenite) gives sharp end points and good differentiation anioiig chlorine, monochloraniine, and dichloramine, and can be done automat,ically. This automatic means of cherking residunl chlorine concentration is described by Hazey (38) in an account of the use of a n automatic Wallace and Tiernan residual chlorine recorder a t the Wyandotte plant,. h comparison of familiar methods of determining free chloriiic concentration was made by Lur’e and Nikolaeva ( 7 2 ) ,who stutliecl the iodometric, methyl orange, arsenite-tolidine. and p-aniinodimethylaniline met,hods. 9 1 1 give accurate results, the aut1ioi.s state, and methyl orange gives t h e best differentiation between chlorine and chloramine.. Houghton ( 4 7 ) studied the effect of pH on the chloririe-chloraiiiirie ratio and outlined analyticd methods for folloii-ing t h e clirniistry of chlorine t,reatment. DISSOLVED OXYGEN
KITR LTE, xwrow4, AND CYANIDE
A colorimetric determination of nitrate ion shon.ing unusual sensitivity is presented by Gritsuya ( 5 2 ) . Hydrostrychnine is used in a solution adjusted t o pH 5 . Interferences w e cont8rolled h y the addition of tartaric acid, malonic acid, and citric acid. llinimum nitrate detectable is 0.02 p.p.m. Blom arid Schwartz (8)describe the use of nickel ammonium sulfate solutions as the animonia absorber in t h e Kjeldahl determination of ammonia and nitrates. Several amine-forming salts Ivere investigated. Iln improved Berthelot procedure for t,he determination of anirnonia is described by Kulenok (56). The author recommends tlie use of thymol and hypobromite in place of phenol and hj-pochlorite. Milne (81) discusses precnutions necessary for the preservation of cyanide in samples of natural water. Protection from oxidation, high pll, and low teniperat,ure are necessary. S E LETIUBl
A selenium procedure which uses complexing agents for the elimination of interference a t moderate levels and requires distillation only at’ unusually high interference levels is describdd by Lambert’, Arthur, and Moore (62). Final estimation is made spectrophotometrically after r e a d o n with iodide, by measurempnt of absorption of the iodide-iodine complex at) 352 mp, measurement of the color developed wit,h “cadmium iodide-linear starch reagent’,” or precipitation and collection of the &arch blue in a confined spot test apparatus (65). Preparation of t,he st,arch reagent and uses as indicat,or for oxidants and iodide are given in other papers (60, 6 1 ) . -4colorimetric selenium determination in which cation exchange i,esin is used for the separation from interferences is descrihed bjToshino (1%’). Selenite passes t,hrough quantitatively a t pH 0.7 t o 5.0. Separation from zinc is excellent, but iron cannot exceed ten times the selenium concentration. Selenium can be “gat’hered’’b y coprecipit’at’ionwith zinc hydroxide and then separated from zinc in the cation exchange column. Vanossi (229) presents a selenium determination in which the free element is concentrated by collection a t the water-chloroform interface after distillation. 4 s little as 0.1 microgram of selenium can be detected and t h e author suggests a lower limit of 0.01 microgram by using t h e catalytic effect of selenium on the reduct,ion of gold by stannous chloride. FREE CHLORINE AND CHLORAMINES
llarks, Williams, and Glasgow (77) point out the essential advantages of the amperometric determination of free chlorine
I n tlie continuing se:irc,h for improved determinations of dissolved oxygen, a careful study of t h e aceid-chromous niethotl by Stone 2nd EichelLergrr appears t o have consideral~lcsignific-ance (121). Dissolved oxygen rewts to gire t r i i d e n t chromium. Iodate is added in excess to react with the exce:s of chronious ion and the unrencted iodate is ronverted to iodine and titmted n-ith thiosulfate in prcwiice of starch. The eliniiriation of nitrite interference is descril)ed. ( ‘ h e c k against very cai,eftdl>- prepared standard oxygen solutions give excellent agreement Tx-ith the values adopted by the American Public Health Associatioil. T*erhestel, Berger, and Royer (150)report a crhical study of dissolved oxygen deterniiiiations suitable for concentrations in the 0.01 p.p.ni, rxige. The \Tirikler method was unsuitalile a t these extreme dilutions. -411 improved spectrophotometric otolidine procedure is recommended. Oxygen-free water was prepared by use of a cation rschange resin containing copper. A polarographic determination is reported by Seaman and -4llen (116),in which the diffusion current is measured before and after deaeration with nitrogen. Potassium chloride is used to raise the conductance, suppress the diffusion current maxima, and minimize the effect of variat,ions in natural conductance of samples. illarch (76) describes in detail, sufficientt o permit reproduction from data given, a port’ahle, polarographic dissolved oxygen meter using a rotating plat’inum electrode. The instrument was designed for nat’ural brines and the aut’hor reports that to date att,empts t o use the instrument with natural waters by adding sodium chloride in sufficient amount t o raise the ionic content to brine values have not given satisfactory results. Good linearity is reported in checks made b y diluting brines with deaerated water. Young, Pinckney, and Dick (135) made a study of the Kinkler method, Schwartz-Gurney modification, and potentiometric methods and recommend the use of potentiometric determinat,ions. Ot,her studies are reported by Splittgerber et al. (123) and Meyer and Brack (80). A paper describing in considerable det’ail the comnionly used methods was given b y Leclerc, Beeckmans, and Beaujean (66). OXYGEN CONSUMED A S D BIOCHEMICAL OXYGEN DEMAND
A publication by illoore, Ludzack, and Ruchhoft, (86) appears t o be a significant contribution toward easing the chronic state of uncertainty in the determination of t h e “oxygen-consuming” power of natural water. The authors made a careful statistical study of the permanganate, iodate, chromate, and chromate
ANALYTICAL CHEMISTRY
298 plus silver sulfate methods. Both pure organics and trade wastes were used as standards for comparison. T h e authors’ results, obtained with t,en replicates on each run, show the superiority of the acid dichr0mat.e method using silver sulfate catalyst as recommended by Muers (84)from the standpoints of reproducibility and average percentage of theoretical oxidation. TTO sources report t h a t t h e acid-chromate procedure gives reasonably clos’e agreement with t,he 5-day B.O.D. values. Chakravarti and Som (16) compared the t,wo methods on three types of waste and found slightly higher average results by acid chromate. T h e difference is attributed t o presence of humus, cellulose, and other substances that are not oxidized biologically. T h e y also studied the effect of temperat,ure on the acid-chroniat,e method and found a nearly linear increase in oxidation rate n i t h temperat’urebut wide variation in rate of increase between various kinds of wastes. Rhame (109) made similar comparisons between “oxygen consumed” by acid-dichromate and B.O.D. and found good agreement when an ammonia correction was made. Aledalia (79) studied t,he application of the autoxidation reaction of organic groups in the presence of hydrogen peroxide and ferrous ion as a possible oxygen consumed method. Oxidat,ion was far short of theoretical in all tests with knowns and the method in t h e present state of development seems suited only for qualitative detection of presence of organic matter. Sensitivity for trace amounts of organic matter is good. T h e author studied t h e acid-chromate-silver sulfate method and permanganat’e method also as means of comparison; results show about 60% of theoretical oxidation on t,he average x i t h the former method and the unusually ]OK figure of less than 10% oxidat’ion with the latter. Pirogova (97), using an alkaline pretreatment, reports oxidation ranging from 65 t o 90% of theoretical in the permanganate determinat,ion of oxygen consumed values for solutions of carbohydrates, proteins and fatty acids. Two authors have reported on t h e t,oxic effect of traces of metals on t h e bacterial decomposition of waste. Heukelekian (42) 3tudied the problem using both the dilution method and direct oxygen consumption. Dawson and Jenkins (20) used the Karburg manometric al)parat,us and reported highest toxir,ity with zinc, copper, rhromium, cadmium, and nickel. Anions and organics were studied and in general tosic effects were not noted. Other st,udies are reported b y Skoliintsrv and AIikhailovskaya (lal),Malehow-Mgllei- (76), Van Neter, Gerke, and Buswell (1,i, 128), and Porges and co\vorkerx (100). ORGANIC RIATTER
A significant st,udy of the nat,ure of organic pollutants in natural water is presented by Braus, Middleton, and Kalton (11), who have made t,he first extensive effort, t o apply t,he systemat’ic methods of organic qualitative analysis t o the characterizat’iori of organic compounds in water. Organic matter was collected by adsorption in tanks containing activated charcoal. T h e flow of water through the tanks was metered. -1considerable range was found in the adsorption efficiency of commercial brands of charcoal. Organic matter was extracted from the charcoal with ether, lyeighed, and then subjected to qualit,ative analysis according t o the scheme of Ehriner and Fuson. T h e presence of phenols, rosin-type compounds, pyridines, pyrroles, and aliphat’ic hydrocarbons as established. T h e application of infrared spectrophotometry to the determinat,ion oil and phenols in nxter is reported by Simard el al. (120). Use of infrared permits the determination of as little as 0.1 p.p.m. of oil and 10 p.p.h. of phenol. Phenols are determined by bromination, followed by extraction with carbon tetrachloride. Because of the high affinity of the lower molecular weight phenols for water, it is not possible to make a direct extract,ion with omission of the bromination step. T h e absorption of the extract is measured at, 2.84 microns for the phenol deter-
mination and a t the 3.4-micron region for oils. For calibration purposes standards should be prepared from synthetic mixtures that approximate the composition of the oil pollutant as closely as possible. When composition of the pollutant is undetermined, the authors recommend the use of an iso-octane, cetane, and benzene calibration mixture. Using this mixture, difficulties are encountered with lower aromatics because of t h e weak C-H aromatic absorption in the 3.4-micron region. Musante (87) describes a significant modification of the conventional benzene extraction-evaporation procedure for the determination of oil in water. It is shown that enormous losses occur through prolonged heating past the point of complete removal of benzene solvent. Distillation is recommended for solvent removal, and a procedure is given which involves a preliminary macrodistillation for removal of the bulk of solvent, followed b y microdistillation. It is not possible to attain complete removal of solvent; hence a blank is always run. Recovery with knowns ranged from 72 to 136% with an average of 102.6%. RADIUM, RADIOACTIVITY, A h D URANIUM
The separation of radium from barium and other elements is described b y Tompkins (127). T h e sample is passed through a cation exchange resin and the radium and barium are eluted fractionally TT ith solutions of various saturated polycarboxylic acid salts. The fractions are analyzed radiometrically. An outline of methods used t o estimate radiometric strontium, barium, cobalt, and iodine is presented by Duncan and coworkers (22). I n general, the methods are conventional. Strontium and barium are brought down as chromates and converted t o carbonates for counting. T h e cobalt is separated by extraction as the thiocyanate in amyl alcohol-ether, and is converted t o ferrocyanide for counting. Iodide is precipitated x i t h silver for counting after extraction v ith carbon tetrachloride. Fields and Pyle ( 2 7 ) present a survey of the fundamentals of determining the micro quantities of radioactive isotopes found in natural waters. The techniques involved in the determination of a typical alpha and beta emitter are discussed in considerable detail, using uranium as the example of a typical alpha emitter and iodine as the typical beta emitter. Fluorometric deiermination of uranium concentration by “gathering” and pulse analysis are discussed. T h e discussion of the beta emitter covers use of a “carrier,” conditions for accurate count, corrections for back-scattering, beta absorption, background beta emission, etc. Gubeli-Litscher and Kolb (34)discuss determination of radium and thorium in spring waters. The sample is equilibrated \%ith the gaseous phase by continuous circulation in closed system and the activity of the gaseous phase is measured in ionization chambers. The same type of determination is discussed in detail by Fineman and coworkers (28),viho use a stream of argon for sweeping the radon into the alpha-ionization chambers. TTT o papers offer ideas and information useful t o anyone dealing with radioactivity in water, but have only an indirect analytical significance. Eliassen and coworkers (24) discuss the removal of dangerous isotopes by column techniques, and Lauderdale and Emmons (64) assess the value of conventional treatments in decontamination of public supplies. A new chemical test for uranium is reported by Dasgupta and Gupta (19), who used oxalohydroxamic acid for the quantitative determination. An orange color is measured a t 420 mp. Limit of identification as a spot test procedure is 0.2 microgram and the dilution limit is 1 t o 240,000. Kakanishi (88) describes the microdetermination of uranium by means of fluorescence in a sodium fluoride bead. Limits of detection are 0.1 microgram photographically and 0.001 microgram by visual comparison with standard beads. Maximum fluorescence is a t 555.4 mp. MISCELL4iYEOUS
A boron test of unusual sensitivity is presented by Hegedus (89).
V O L U M E 2 4 , N O . 2, F E B R U A R Y 1 9 5 2 T o 1 ml. of sample add 16 ml. of sulfuric acid and heat to fumes. Cool below 100" C., add 2 ml. of azo dye (0.12 ounce of chromotrop 2 B in 500 ml. of sulfuric acid), dilute with sulfuric acid t o 15 ml.; keep for 30 minutes a t 100" C., cool, and add 0.04 ml. of sodium cobaltinitrite solution. Shake well and keep for 8 hours in darkness. Read color in photometer. Sensitive t o 0.25 microgram. Jewsbury and Oshorn (49) describe the photometric determination of boron with morin. Interferences and optimum conditions are discussed. T h e range covered is 20 t o 200 micrograms. Ilegedus and Hegedus (40) describe a volumetric determination of arsenic based on the Marsh t8est. About 0.1 p.p.m. of arsenic can he detected. T h e theoret,icalfactor for the ratio of potassium iodate to arsenic gave low results and a n empirical factor was used. Data are presented by Buneev (12) on the determination of dissolved gases in mineral waters. Laboratory analyses of gases are often not accurate. Siiniann (89) gives directions for colorimetric determination of silic:tt,es, organic and inorganic phosphorus, and nitrogen in sea water. llodifications of standard methods are recommended. Field tests for t h e usual sanitary analyses are described b y Schroeder (115) and a port,able field kit and suitable chemicals are presented by Drachev (21). Studies of the silicomolybdate method for high concentrations of silicon in natural vaters are reported hy .$oki (1). l l u n d y , Burns, and Samuel (85) have conducted a review of conventional methods for water analysis. LITERATURE CITED
(1) Aoki, F., J . Chem. SOC.J a p a n , 71, 634-6 (1950). (2, Back, J., and Raggio, J., Rea. ohras. sanit. nacion, 13, KO.132
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[End of Review Section]
TITRATIONS IN NONAQUEOUS SOLUTIONS General and Round-Table Discussions Held by Division of Analytical Chemistry, 119th Meeting, AMERICAN CHEMICAL SOCIETY, Cleveland, Ohio, April 1951
Potentiometric Titration of Salts of Organic Bases in Acetic Acid Salts of Amines, Basic Heterocyclic Nitrogen Compounds, and Quaternary Ammonium Compounds CHARLES W. PIFER
AND
ERNEST G . WOLLISH
Products Control Laboratory, Hoffmann-La Roche, Inc., A-utley, K. J .
T
HE advantage of using perchloric acid for the titration 01 organic bases in glacial acetic acid was first demonstrated bq Conarit and Hall (2, 7 ) . Conant and Werner (3) and Hall (6, 8) determined the strength of organic bases in glacial acetic acid Kith perchloric acid. Hammett and Dietz (9) used formic acid as solvent, while La Mer and Don-nes (15) described conductometric. arid eipctrometric titrations in benzene. Perchloric acid q-as used for the visual titration of amino acids by Kadeau and Branchen ( I ? ) mith crystal violet as indicator. Blumrich and Bandel ( 1 ) applied perchloric acid titrations in glacial acetic acid for the determination of primary, secondary, and tertiary amines, aliphatic bases, and alkaloids. Fritz (4, 6) titrated many organic bases in nonaqueous solvents with perchloric acid in dioxane o r acetic acid. Palit (18) determined alkali metal salts of Keak monobasic organic acids in a mixture of solvents by perchloric acid titration. Titration of Salts of Organic Bases (except hydrochloric, hydrobromic, and hydroicdic acid salts). Plati and Ingbernian (20)reported that organic acid salts of organic bases could be titrated potentiometrically in glacial acetic acid n ith perchloric
aritl. AIarkunas and Riddick (16) investigat,ed the titration rarhosylic a,cid salts in glacial acetic acid and titrated bases m d salts of weak acids. T h e aut,hors found t,hat salts of organic bases with strong acids other than halide acids could also be titrated ~otentio~net.rically. Titration of Halide Acid Salts of Organic Bases. Halide arid salts could not be titrat,ed. [After t,his manuscript had been \\-ritten, two papers by Higuchi and Concha (10, 11) appeared, in which the visual titration of alkali chlorides and hydrochlorides Lvith perchloric acid is described; tmhereaction is driven to cornpietion I)? repeated boiling. IIiguchi and Concha also studied the tiehavior of some inorganic anions in glacial acetic acid. ] The authors' main objective was the development of a procedure to overconic= this obstacle, as most of t,he physiologically active conipc~und~ are prepared as their water-soluble halide acid salts and a method for their direct titration was highly desirable. They \yere able t o titrate halide acid salts of organic bases with perchloric acid by potent,iometric*or visual procedure after converting the salt to the acetate through the use of mercuric acetat e (if
