REPORT ON 'riI5: PROGRESS OF ANALYTICAL CHEMIRTRY,
527
Reports on Special Departments of Chemical Science. REPORT ON
THE
PROGRESS OF ANALYTICAL CHEMISTRY,JULYTO SEPTEMBER, 1879. BY QIDEON E. MOORE, PII. D.
I. ATOMIC U'EI(+HTS O F THE ELEMENTS.
DUBIAS (Compt. Rend., 86, 65, through Zcitschr. f. anal. Chem., 18, 508) communicates several very interesting and important facts on the preseme of oxygen in inrtnllic siluer. H e finds, namely, that 1 kilo of pure silver, when heated t o 500-600° C., gives off 57 C.C. of oxygen. If it has been melted with nitre for 15 minutes, in the air, it gives off 168 C.C. or even I74 C.C. oxygen. Iri the determination of the equivalent weight of silver, when i t has been melted with borax a n d nitre, and granulated with access of air, the presence of oxygen in t h e product exerts a mkterinl influence on the accuracy of the results. Thus, the proportion of silver t o chlorine, determined by Stas, becomes 108 : 35.50, instead of 108 : 35.47. Dr. TELLEF DAHL(Chem. News, 40, 25) states the eyuivalent of rbormegium, the new metal discovered by him in copper-nickel from Kragerij in Skjaergaarden, to be, apparently, 145.9. T h e color of the metal is white, with a slight brownish cast. I t has, when polished, a perfect metallic lustre, becoming tarnished after some time. It has about t h e hardnesR of copper, and may be flattened in a n agate mortar, Melting point, 850' C.; sp. gr., 9.441. Only one oxide, NgO, has been obtained. W i t h hydrogen i t gives a brown sulphide, even in strongly acid hydrochloric solutions, soluble in ammonium sulphide. T h e solutions of t h e metal are blue, becoming greenish on dilution. T h e sulphuric solution turns brown on addition of zinc, and t h e metal is deposited in a pulverulent state.
A. GUYARD (Moniteur Scientifiqoe, Quesrieville, July, 1879, through Chem. Newu, 40, 57) has determined the atoinic weight oj' uralium, the metal discovered by him, in 1869, in Russian platinum, t o be 187.25. It is, next t o silver, t h e whitest metal known, more ductile than platinum, which it equals in malleability, soft as lead, and possesses a melting point near that of platinum, a sp. gr. = 20.25 ; atomic volume = 6.25. I n its chemical properties it is difficult to distinguish from platinum.
528
KKPORL' ON T H E 11.
I'ROGRESs
O F A N A L Y T I C A L ClIEMIIS'I'R~
G E N E R A L I N O R G A S I C ANAI.YSIS.
A , Qrtah/atizv>.
E. P U R W T T I (Gaze. Chirn. Ital. and kh-1. Uer., 11, 1,24P, through Zeitschr. f. anal. Chem., 18,4 i G ) reconinlends ti7icture qf'gu(citrc*tin~ (IS a reageict,fo/* copper. According t o the author, even v e r y dilute solutions of cupric chloride are reduced t o ciiprous cahloride b y this reagent, with prodiwtion of a blue tirit. A s most oxypc.n salts o f coppw undergo double dc~cornpositioiiwith foi~matioi~ of c~riliricchloride, w l i t ~ 1 1 bronght i n contact with a solution of an alkaline callloride, t l i c ~;tiitlior adds the latter before testing. If 1 c.c. of solution contaiiiing ,&o ingriii of cupric sulphak, be mixed wit,li a solution of an alkaline chloiklt~, and allowed to flow down the sides of :I vessel containing alcoliolic. tincture of guaiacum, the blne color is distinctly perceptible. l k i u rich Fresenius remarks to the foregoing that Purgotti's otiservxtions are not new, having been anticipated 1)y Srhoenii (Zeitachr. f. an:iI. Chem., 9, 210) i n his paper on the use of tincture of guaiac~unias :t reagent. E. J . ( ' H A P X A X (Cheni. Xews, 35, 13, 26, 36, throng11 Zeitschr f. anal. Chem., I&, 4 i i ) has pronounced the well kriown Y'ur)iei*'s rec,c*tioil ,for b o r m i c trrit?, by examining t h e color communicated to the flame I y adrnixtui-e of the substance with a mixture of 4 3 parts potassium acid sulphate a n d 1 part calcinni fluoride, to l w wortlilesa, as it gives no result with sodium horate, and as the other borates give the reaction without the flux. 1.'. Le Neve Foster (idem, 35, 12;) shows, on the contrary, that even a niixture of 99 parts sodium cliloridc. and 1 part sodium borate, will give a distinct green flame rractioii. B.
Qtraulifalizc~.
ALEXANDER ('LASSEX (Zeitschr. f. anal. Chem., 18,3 7 3 ) has developed n /Lei0 nLetJiod qf ytctriititntice niicilysis sitsceptihle oj' ? L I I I ) W Y ous applictrtio/ts, froin the principle on which is hased his method of separating ferric oxide and alumina from manganese, etc. (idem., 18, 173 and 189, and this JUURSAL, I, 3 2 5 and 3 2 7 ) . The estiirtcrtioii of' )ritry/2esirc is hased upon the facat that niagliesium forms a soluble double oxalate with potassinin or ammonium oxalate, which, on the additiori of acetic acid, is decomposed, with separation of magnesiuni oxalate. 'l'hr quantitxtivc separxtiori o f the magnesiuni is effected by adding t u the solutioii, \vhic.h sliot~ltl measure about 2 5 c.c., a hot saturated solution of arnrnoninm oxalate, or kjy di.,sol,iiip witli the aid of heat the solid anirnoninni osalatr therein. Wlien sutticient cjf thc reagent has been xcltlecl, the solution
REPORT ON THE PROGRESS OF ANALYTICAL CHEMISTRY.
529
is perfectly clear. On adding t o the boiling liquid an equal volume of 80 per cent. acetic acid, and boiling, with stirring, for a few minutes longer, a heavy, cryRtallitie precipitate of magnesium oxalate forms, and Rettlen rapidly t o t h e bottom of the vessel, when the ebullition is discontinued. Small quantities of magnesium precipitate only after some time. I n all cases the liquid is kept in a covered beaker for about 6 hours, at a temperattire of about 50' C., then filtered, and the precipitate washed completely with a mixture of equal volumes of concentrated acetic acid, alcohol and water. The precipitate is enveloped in the filter, and converted by ignition in a covered platinrim crucible i n t o magnesium oxide. T h e heat employed must be very gentle, as long a8 vapors are evolved, and must not be raised until the cover has been removed, and the carbon of the filter has become entirely consumed, and t h e residue white. The conversion t o oxide is then completed by exposure t o a red heat. A series of 34 closely accorda n t determinations by the author, using from 0.0377 t o 0.2075 g r m of pure magnesia, gave an average result of 99.41 per tent. T h e presence of ammonium chloride materially interferes with the accuracy of the determination, the analytical results of the author showing tbat the loss of magnesium is, t o a certain extent, proportional t o the ratio between the ammonium chloride and magnesium present.
The sepuration of rnagneRinf r o m the alkalies by this method, may be effected in solutions of t h e chlorides, sulphates or nitrates; the solutions must, however, be more dilute than in the preceding instance, owing t o the tendency to the formatinn, in concentrated solutions, of double oxalates of magnesium and the alkaline metals, which are not decomposed by t h e further treatment of the precipitate. If, however, the liquid be diluted t o about 5 0 c.c., and treated in the cold with a cold saturated (1-24) solution of ammonium oxalate, the magnesium oxalate may then be precipitated in such a state of purity, t b a t it is only with the help of spectral analysis that t h e imponderable traces of the alkaline metals may be detected therein. T h e precipitation from more dilute solutions cannot, however, be effected without a slight loss. B y the addition of about 4 volume of alcohol t o t h e cold liquid, after the precipitation of the magnesium oxalate, almost the whole of the magneAia is obtained. The magnesium oxalate, thus precipitated, does not show in the spectroscope a larger proportion of the alkali metals than that precipitated without alcohol. T h e analytical results obtained by the author are eminently satisfactory. The separation of ferric oxide a?,d alumina jrorn manganee, zinc, cohalt and nickel, by the older methods (precipitation as basic
acetate or oxide), is tedious, and in the case of the t h e metals last named, imperfect. It is necessary to reiteat the precipitation wherever accuracy is required, but, in the case of cohalt and nickel, even after five-fold precipitation, the filtrate still gives the rcaetioiis for tliose metals. In a mixture containing I.:]; E r i n ferric oxido, : ~ n d 0.1454 grin metallic* cobalt, th(j xiitliur o1tt:iined b y ~ l o u h l e [)recipitation with miiiioniuin c.:tr.lmi:ttc, but i4b per (wit. of thv cohalt taken. A similar er1)oiiiicrit \\it11 0 . 1 8 0 ~ grni irickel ant1 I . % g r m feriic oxide, gavc 99.2 pw w r i t . of t l w ;iniouiit of tliv foriner taken. I n :L tfmchle precipitation with sodiurri acet:itv, tht. loss of nickel amounted to 4 . ~ 1pel. rciit. The seltaration of 0 . 2 2 4 j grrn of zinc oxide from 1.35 grin ferric- oxidc, yieltled, by oiie precipitation with arnmoniiini carboiiate, Rti.:iB 1)er cent. of the former. Th(1 separation of 0.2ilI.1. g r m zinc osidc from l . : < ~g i ~ nferric oxitle, b y one Imcipitation with sodium acetate, yielded hut $44,; i pw ctmt. In tlie previous communication above cited, tlie autlior has miriutrly indie:itcti the precautions requiretl in tlie separation o f w t r n y u i t e s r as oxalate, with addition of zinc c*liloritle ; his more rtLc.c.rit rt?sc~arclie~ have sliown that tlie latter siibstarice iriay, with the iiiost satisfac:t,ory or c.alciurn c4iloritle. Z n order results, 1)c replacwl h y ni;~gnesiun~, that the m a n g a m w shoriltl be present i r i ttica wsidue in the state of M I I ~ O :it~ , is ~iccessary tliiit for each inolrc.rile uf rrianganic: oxictc. there ehoultl be prcscnt r i o t less than one iiiolwiile of niagnesiurri, calciurii oxide, other the resitliic of ignitioii will cwntain mangaiio~u-riiarigarric oxide. T l i c iinalyticd results obtiiirie(1 l)y the aiitlior are c.xti.cirielj- satisfactors ; :ih i ~ i i iiistaricr, I will b t , : i t t A tliat a mixt,ure cont:tiniiig in:tiiganoris oxide, ~ 1 . 0 . j grm, ferric oxide, O.:jtj grni, grm, :tnd phosaluiriina, 0.2 I p i n , magnwia, 1.H grm, lime, 0.0 phoric anliytli.idc, 0.01 6 grni, yiel(let1 maiig:tnons oxitltd. 0 . 0 ~ 0 7 grni. In the separation of ziitc', it is indifferent \vlicther tlie riwtal ht. 1)re"ent as chloriilci, broinide, nitratr or si1 ate, iiltlioiigli, i i i t t i c 1:ittc.r case, owing to the low solubility of pot i u r r i sulpliate, tlie w l u t i o i i should be more dilute t l i : i i i would othcrmisc br iiec.c:ss:iry. I n :ill c:;isw, tlrca frec acid must be conipletely expelled b y csv;tpor:ttioii, t tie siihstaii(3c moisteiied \\itti a few drops of iiitri(4 acid, : t i i d digebtcB(l iii the iv:itcrbath for a short time, t,o iiisure the coriiplcttr oxit1:itioii of tlir iroii. About, seven times the weight of the IO 1: 13.M I : i p i e 00 1 : 13.00 1: 1:
m.5.00
245.00
I : w.00
DIFFERENCE.
:'r$h$:;
0.0170grm
tU.0013grrn
O . O I I ~* '
+o.m~
0.06oO 0.0183 0.0160
"
-0.oo04 '*
'*
-0.0029
a'
"
$0.0015
"
n,om
1'
+0.0007
REPORT ON ,riiE PROORES OF A N A I ~ Y T I O A LCHEMISTRY.
Second Series. MIXTURE T A K h N -.-
Phoahorlc Anhydride. 0.0199g. 0.0089g. 0.0230~. 0.0116g. 0.0330g. 0.0166g. 0.0172g. 0.0238g. 0 . O . g . 0.0128g. O.OW3g. 0.01wg.
CONTAINING. Ferric Oxide. 0.738g. 0.736g. 0.7Zg. 0.005g. 1.470g. 0.153g.
Alumina. 0.429g. 0.mg. 0.21Sg. 0.6aSg.
Lime.
0.2Oog. 0.mg. 0.Oolg. 0.445g. 0.005g. 0.IRjg. 0.865g. 0.155g.
-
FOUND. DIF'K'NCE.
Magnesia. P205 : M O
%%%~
0.005g. 1:69.00 0.0260g. 1:101.00 1:89.00 1:92.00 0.185g. 1:77..W
0.mg. 0.Oolg. 0.445g.
0.U75g.
533
1:%.10
0.0103g. 0.0114g. 0.0153g. O.oU9g. 0.0198g.
+0.0061g.* +o.ooosg. +O.oozSg. -0.oo9og.
+0.001lg. +0.00lOg.
Arsenic acid may be separated (e. g., from cobalt, nickel m d zinc) in the same manner as phosplioric acid. I n applying the foregoing method to the determination of phosphorus in cast iron, the author recommends t o dissolve in a dilute solution of bromine in hydrochloric acid ; the solution is evaporated t o dryness, ant1 t h e silica separated as usual. I n order t o separate t h e iron after i t has been converted into potassio-ferric oxalate, t h e hot concentrated liquid is, after addition of acetic acid, allowed t o cool ; the greater portion of t,he ferric double s d t thus crystallizes out, the residue is precipitated with alcohol. Tlie olwration is much more rapid and convenient than that with ammotiiuni molybdate. T h e author communicates n u n i e r o ~ scases to illustrate the adaptation of his method t o special technical problems, for which the reader is referred to t h e original. F. BEILSTEIN and L. J A W E I N (Bcrl. Uer., 12,1,628) communicate t h e following )Lei0 ritetkotb f o r the direct xtpci*rrtioic c.f vna)iynarse j f o m i r m , whirh appear t o iinitc the c.onditioiin of extreme siniplicity and rapidity of execution, with a high degree of accuracy in the results : First nwtltod.--'l'he solution of the two iiietnls is poured, in the cold, into a concentrated aqueous solution of potassium cyanide, t h e solution is filtered, tlie slight precipitate of ferric oxide which always remains, a n d which does not dissolve on.further addition of cyanide, is dissolved in a few drops of dilute hydrochloric acid, and added t o t h e original solutipn, after adding an excess of cyaiiide solution t o t h e latter. Iodine is added, until the solution assumes a brown color, and then a few drops of alkali t o remove the free iodine. T h e manganese is precipitated, theoretically, according t o the equation : 4KCyMnCy, 141 2H,O = M i i 0 , 4HI 4 K I SCyI. I n practice, however, it is obtained as a mixture of varioum oxides. T o ascertain if the precipitation is complete, a little of t h e clear liquid is treated, first with iodine, and then with potassa or Aoda solution; i t
+
+
* The precipitate contained iron.
+
+
+
ICEPORl ON T H E PROQRESS O F ANALYTICAL CHEMISTRY.
535
nitrate as an indicator, after the method of Volhard (Ann. d. Chem., 190,I , and this JOURNAL, I, 272). If A be the volume of the mixture of zinc and sulphide s o h tions, A,, t h e volume of t h e portion of the filtrate from A taken, B, t h e volume of t h e mixture of A , and t h e silver solution, B,, the volume of t h e filtrate from B, taken f o r titration by Volhard’s method, a,the volume of silver solution, corresponding t o 1 C.C. of sulphide solution, h, t h e quantity of zinc, corresponding t o 1 C.C. of the sulphide solution, n, the volnme of the sulphide solution added, p , the volume of the silver solution added t o A,, 9, the volume of mlpho-cyanide solution added t o Bl, 5, the weight of zinc sought, then, on the assumption that 2 8 , = A , and 2B1=B, we have the value of E b y the equation : (an - 2p 457) b c=-
+
U
No-m:-The foregoing method is much more complicated than that of C. MANS (Zeitschr. f. anal. Chem., 18, 162, and this JOURNAL, I, 329) for the volumetric estimation of zinc by Volhard’s method, and manifestly inferior thereto in essential particulars, especially in respect t o the fact that the precipitation of hydrogen sulphide in acetic acid solution, which forms the first step in the latter method, also insures the separation of the manganese, which is m c h a frequent ingredient in the zinciferous minerals of this country.
J . HERTZ(Archiv. f. Pharm. [3 R.], 14, 322, through Zeitschr. f. anal. Chem., 18, 475) communicates the results of his experience with Vblhard’s wethod,for the determination of silver and the halogens. l‘he author finds t h e method t o be extremely practicable, and that i t combines the advantages of great accuracy, with ease and rapidity of execution. CHARLESA. CAMERON (Chem. News, 38, 145, and Analyst, Oct., 1878, 338, through Zeitschr. f. .and. Chem., 18, 475) recommends the dvternzinution of leud us lead iodute. According to the author, iodic acid and iodates precipitate lead much more completely than sulphuric acid. T h e e d i n a t i o n may be made either gravimetrically or volumetrically; in the latter case, a normal solution of a soluble iodate, standardized
REPORT ON THE PROGRESS O F ANALYTICAL CHEMISTRY.
537
yellow NiS. Zinc may be converted without loss t o ZnS. Cadmizm undergoes a similar change to CdS. Copper gives a sulphide, t h e composition of which is then only Cu& when the experiment is finished with a current of hydrogen. Silver in any form of combination, is readily transformed into Ag,S. Oxide, chloride, carbonate and suiphate of lead, are readily converted into PbS. Bismuth is readily converted t o Bi,S,, by igniting the precipitated sulphide. Antimony sulphide may be freed from free sulphur a n d converted' t o Sb8SS, by ignition a t a temperature below dark rcdness. T h e alcohol flame ia conveirient for this purpose. Tin is converted with greater or less difficnlty t o SnS,; t h e conversion iR not, however, always exact, but may serve t o simplify other methods, e.g., tin solder in readily transformed to a mixture of tin and lead sulphides, which niay readily be separated b y means of hydrochloric acid, etc. A n analogous process serves for the separation of tin from tungsten, WS, being insoluble in acids.
F. A. GOOCII(Proc. Am. Acad., Oct. 8, 1879) has, a t the request of Dr. Wolcott Gibbs, nubjected to an exceedingly thorough investigation, the method f o r the determination ofphosphoric acid as magnmiirm pyrophosphate, with t h e object of ascertaining thc best mode of conducting this determination, concerning which so many conflicting accounts have been published by earlier investigatora. T h e general reualtn attained by the author, in t h e course of 129 determinationR, macle under the most diverse conditions, m e given in his own words, as follows : " It would appear, from t h e preceding account, that in determining the phosphoric oxide of alkaline phosphates, free from sulphates, or other substances likely t o contaminate a precipitate, accuracy is riiost conveniently and surely attained, by adding to the somewhat dilute solution of t h e phosphate, ammonia, in slight, but quit e distinct cxcess, then an exceas of magnesic chloride mixture, contailling no free ammonia (made by dissolving three parts of crystallized magnesic chloride and eight parts of ammoniuni chloride, in water, adding water containing ammonia, until the volunie of t h e solution reaches forty-eight parts, filtering and boiling off t h e free ammonia), and, after the precipitate has settled, ammonia, until the liquid evolves a strong odor of it. I n determining t h e phosphoric oxide of phospho-tungstates, the best resulte are to be g o t b y adding t o the nolution containing free ammonia, an excess of either of t h e magnesia mixtures, washing the precipitate with the precipitant, dissolving in hydrochloric acid, diluting, if necessary, and re.preoipitating with a little dilute ammonia, adding strong ammonia after the pre-
538
REPOET ON T H E PROGRESS OF AXALY1'JCAI. CR h3fJS'TIW.
REPOK'C O N THE t'HOCKESS O F ANA1,T'I'ICAL CHEMISTRY.
539
and re-dissolved in ammonia water. T h e fil tereci solution is evaporated t o dryness, a little watcr added, and re-evaporated, the operation being repeated until the weight is constant. T h e residue then represents a mixture of ammonium phohphate and an arid amrnoniurri molybdate, and contains of its weight of phosphoric. anhydride. 'l'he analytical results communicated by the author, show the method to be as exact as that of conversion to magnesiiini pyrophosphate, while a detcrrnination can be made with it in one day.
SAMUELL. P ~ X P I E(Am. I . I > Chem. Joiirn., I, 27) has devised n new ool~inwtric-wiethorl3)r t h e d(>ter)niicntionq f j k o r i n e based on the conversion of the fluorine into hydrofluo-silicic acid, t h e conversion of the latter to potassium silico-fluoride by treatment with potassium chloride and alcohol, 2nd titration of the hydrochloric acid thub set free. Hydrofliio-silicic :wit1 cmiriot be directly titrated, because as soon as an alkaline reactiori is r e a c h ~ l ,the silico-fliioride is decomposed, and the acid reaction reappears. lhriiini chloride m i n o t be used i n the place of potassium chloride, for the reason that, in tlie former case, the turbidity produced masks the end-rrwtion. T h e potassium silico-fluoride is a very transparent precipitate, and permits the change in color of the litnius to be readily perceived. T h e author proceeds as follows : the fluoride is weighed into a 150 C.C. flask and, unless i t is a silicate, 10 grms of p o dered ~ and ignitrd quartz added. T w o or three pieces of quartz of the size of kidney beans are also introduced, t o facilitate the mixing when the flask is shaken; 30 t o 40 C.C. sulphuric acid, previoudy heated and then cooled, are added, and the flask tightly closed with a doubly perforated cork. Through one of the perforations is passed a tube, by means of which dry air from a gasometer IS conducted to the bottom of the flask j through the other, a tube connected with a Utube 5 m.in. in diameter, kept cool by immersion in a beaker of mater, t o retain any sulphriric acid that may Come over, conveys the mixture of gas and air to a plain U-tube, 18 c.m. long and 2 3 c.m. in diameter, containing a mixture of equal volumes of a solution of potassium chloride and alcohol; after bubbling through this, the gas passes through a second smaller U-tube, where the last traces of acid are ahsorbed. T h e decomposing flask is placed on an iron plate, heated by a lamp, and by its side is placed a second flask, containiiig sulphuric acid and a thermomctcr so supported that its brill) is'imniersed in the acid. T h e lamp under the plate is placed midway between the two flasks, and the temperatrirc maintained constant between 150' arid 16G" C. I n ordinaiy cases the decornposition lasts two hours, during which time from 5 t o 6 liters of d r y air are forced through the apparatus.
540
REPORT ON T H E PROQREfiS OF ANALYTICAL CHEMISTRY.
After the decomposition is finished, the acid may be titrated either in the two large U-tubes, or t,he contents of the latter may be first transferred into a beaker, and the tubes rinsed out wit11 alcohol and water (equal volumes). I n order that the ctlcohol at the cntl of the titration may make u p one-halt’ of the vol~itneo f tlw liquid, add a f e w cubic centimeters before titration, o r use a staritlard alkali, of which one-half the rolurne is alcohol. If the mineral writains c.liloriiic~,there is suhstituterl for the empt>- tube one filled with fragments of pumice imprcagnated with perfectly anhydrous cupric. sulphate. In the calculation of the results, every single cyuivalent of soclirim carbonate is equal t o one of hydrofluo4licic acid, or six of fluoriiie, according t o the proportion : Xol. wt. of N%,CO, Mol. wt. of 6FI. Anit. Na,CO, Anit. F1. 106 114 .1 : x The analytical results obtained by the author with pure fluor spar are in the highest degree satisfactory. A. Cor.sox (Bull. Soc. chini. de Paris, 32, 115) recommends that tlw deteriitbnation qf sulphur j i i certciin nuticral sulphirrets, etc., should be effected by combustion i n oxygen, and coridiiction of the evolved gases into a titrated solution 6f sodium hydrate contained in Liebig’s potash bidbs. T h e anterior end of the combustion tube is washed, and the washings, together with the contents of the bulbs, are brought to a detinite voluine; the sulphurous acid in one aliquot part is estimated by titration with iodine, after addition of hydrochloric acid; in another, after addition of sufficient iodine solution to oxidize the sulphurous acid, the excess of free alkali is determined by titration with litmiis and staiidnrd acids, or t h e sulphurio acid therein may be determined hy t,itration nrith barium chloric~eand sulphuric acid. NoTE.-It would seem tlint the oxidation of the snlphuroiis acid in the foregoing method might, \vith great advantage, bc effected by hpdrogen peroxide, which is now a n article of commerce, and has been recoriirriencleil for similar applications, b y G. E. Davis (Chem. Kews, 39, 221, an(l this JOURNAL, I, :1:
