SOLVENTS FOR USE WITH THE MUNROE CRUCIBLE, BY OTIS D. SWKTT. Received June
14,
rgog.
Although when in using the Munroe crucible a succession of determinations of the same analytical radical in similar substances and by a uniform method of analysis are to be made, the analytical product may be allowed to accumulate in the crucible, yet if there be any variation in the analytical material or process the "residue on ignition" must be removed from the felt between each determination. In some instances a part a t least may be shaken or blown out, but the felt can be completely cleansed only by the use of solvents, and this method of procedure is an essential feature of the use of the Munroe crucible in such determinations. The selection of solvents involves several considerations such as the effect of the solvent, either alone or in the presence of air or the solvent product, upon the platinum, and its capacity to easily dissolve the "residue on ignition" and to form mith it a solution which is readily and completely removed from the felt. Q'hile the solubilities and properties of platinum in platinum ware have been widely studied, and precautions to be taken in its use are to be found in the literature (tide Prescott and Johnson, Qual. Chcnz. . 4 ? d y s i s . 1901,p. 95), yet the peculiar properties of platinum in a finely divided state, as it exists in platinum felt, have not been studied further than as to its catalytic action. In
SOLVENTS FOR USE WITH THE MUNROE CRUCIBLE.
92 9
the application of the various solvents for removing precipitates from the felt in the Munroe crucible, certain solubilities of the felt were observed which are not exhibited by solid platinum. The finely divided state and catalytic action of platinum in the felt suggest causes for its modified properties. Of the solvents used to remove precipitates from the felt, hot concentrated sulphuric acid and hot hydrochloric acid, if used alone, cause a decided loss of the reduced platinum, the former by rendering the platinum colloidal, in which condition i t is readily carried through by the wash-water (Phelps), and the latter by taking up the platinum as chloride (presumably by reason of the oxidation of the hydrochloric acid by the dissolved oxygen in the presence of reduced platinum which acts as a catalyzer). However, both these acids, and even fuming sulphuric acid, as well as a mixture of concentrated or fuming sulphuric acid with concentrated hydrochloric acid, may be used freely in the crucible without causing the slightest weighable loss of platinum, provided the following additions are made to the several solvents, as indicated: Ammonium salts, alkali or ammonium nitrates, or nitric acid, to concentrated or fuming sulphuric acid; ammonium salts, other than the nitrate, to the mixtures of concentrated or fuming sulphuric acid with hydrochloric acid, the practice being to add solid ammonium chloride to the sulphuric acid, thereby providing both the hydrochloric acid of the mixture and the required ammonium salt; and ammonium chloride, or oxalic acid or like reducing agent, to hydrochloric acid. With a view to the general application of the-Munroe crucible in gravimetric analysis, suitable solvents will now be given for the various precipitates, in condition for weighing. Many of these solvents have long been known, but are given here because they are suitable for use with platinum felt, while the other solvents were found in the course of investigation, In the following list appear the various solvents used with reference numbers by means of which the proper solvents may be designated for the precipitates, an alphabetical list of which follows next after the list of solvents:
Solvents. (Salts are applied in aqueous solution unless otherwise specified.’) \Tater. 2. Alcohol. 3. Carbon disulphide. 4. Sulphuric acid with nitric acid or nitrates. 5 . Sulphuric acid, concentrated or fuming, with ammonium chloride. 6. Nitric acid. 7 . Carbon dioxide in aqueous solution. I.
Acetic acid. Oxalic acid. IO. Hydrochloric acid with ammonium chloride or oxalic acid. I I. Hydrofluoric acid. 1 2 . Potassium hydroxide. I 3. Sodium hydroxide. 14. Ammonium hydroxide. 1 5 . Potassium sulphide. 8. 9.
930
GENERAL, PHYSICAL AND INORGANIC.
Potassiuni sulphide, yellow Sodium sulphidr. Sodium sulphide, yellow. Ammoniuni sulphide. .\mmoniurn sulphide, yellovr , Potassiurii li~ulpliitc. Sodium thiosulphatc. Xmmonium sulphate. Xmmonium nitrate. Sodium hydrogen phos~iliatc. r\iiiniuniuni oxalate. Xrrnnoniuni acetate, nlkuline. A+iiinioniunit:irt ~ i t ealkali , iir 1’0 t assiuni carl)uiia te. Sodiuni c:irlionnte.
l’~J1:isSiulnchlorate. .-2iiiinoniuni carbonate. I’utassiuin chloride. I’otassiurn iodide. Sodium chloride. .%nimo~ii~iiii chloride. Ammonium fluoride, d r y Calcium cliloride. Magnesium chloride. IJotassium cyanidr. F’errous sulphatr. Silver nitrate. I,rad :icetale. Mercuric nitrate. Ferric acetate.
Solvents for Precipitates in Condition for Weighing. (Xumbers indicate correspondingly numbered solvents in the preceding list. Hyphens indicate suceessive treatments; commas indicate alternative treatments. Ahbreviations: 11 == h o t , c =- concentrated, d = dilute.) Precipitates.
Solvents.
Aluminum oxide . . . . . . . . . . . . . . . I. zc11-1-rc1,r ~ c l i -.IIO. Ammonium arsenomolybdate. . . . . . . 14. Ammonium chloride. . . . . . . . . . . . . . .I h Ammonium magnesium arsenate. . . . G , I o Ammonium phosphornolybdate. . . . xh, 1 2 , 13, 75, 2 6 , 20, :io, 36 Ammonium chlorplatinate. . . . . . . . . . 111 . . . . . . . . . . . . . . . . . ..6-I-lL> tasulphitle. . . . . . . . . . .1411 Antimony tetroxide. . . . . . . . . . . . . . .ioch Antimony trisulphide. . . . . . . Arsenious sulphide.. . . . . . . . . . . . . . .1 2 , I,;, 1.5, 17, 2 1 , 20, 30 Barium carbonate.. . . . . . . . . . . . . . . .;, 24, 30 Barium carbonate, ignited. , , . , . 111, fit1 Barium chromate. . . . . . . . . . . . . f ~ ,io Barium silicofluoride. . . . . . . . . . . . .$J Barium sulphate.. . . . . . . . . . . . . . .,411, j l i Bismuth. . . . . . . . . . . . . . , ,fd Uismuth cnrl~onate( h s i c ) . . . . . . b , I , ) iiismuth clironiate (basic I . . . . . . . (1 Uisrnuth nitrate (basic) . . . . . . . . . (I Bisniuth oxide. . . . . Bismuth oxychloride. . . . . Bisniuth sulphide. . Cadmium carbonate., . . . . . . . . . . . . Gd, 14 ,
Calcium carbonate.
,
...
Calcium fluoride. . . . . . . . . . . . . . . . . -4 I , ~ O L \ C\aIciiini oxalate. . . . . . . . . . . . . . . . .. O ,7 2
SOLVENTS FOR USU WITH THE MUNROE CRUCIBLE. Precipitates.
93 1
Solvents.
Calcium sulphate 23dh Chromium oxide.. . . . . . . . . . . . . . . . . 6 c h + j 1 d r y + 4 z or 4 j , 31dry h +
I,
4sdry h3-6
. . . . . . . . . . . . . . . .6 . . . . . . . . . . . . . . . , 2 3 , 24, 36 ... . ~h Cobaltous sulphide. . . . . . . . . . . . . . . .4c, 5 , 8c, IOC Cupric hydroxide.. . . . . . . . . . . . . . . . h , IO, 14
Gold . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Iron Iron Iron Iron
4c
formate (basic). . . . . . . . . . . . . . . I O hydroxide.. . . . . . . . . . . . . . . . ..6d, ~ o d oxide . . . . . . . . . . . . . . . . . . . . . . . ~ o c phosphate.. . . . . . . . . . . . . . . . ..IO,45
Iron sulphide. . . . . . . . . . . . . . . . . . . ..4,IO Lead arsenate . 1,ead carbonate.. . . . . . . . . . . . . . . . .6d Lead chloride . . . . . . . . . . . . .Ill . . . . . . . . . . . . . 6, I Z
och, 6~11,2 2 , Lead sulphide. . . . . . . . . . . . . . . . . . ..6c, IOC Magnesium oxide. . . . . . . . . . . . . . . .4d, . 6d, ~ o d Magnesium phosphate.. . . . . . . . . . ..6, IO Magnesium pyroarsenate. . . . . . . . . . . 6 , IO Magnesium pyrophosphate Magnesium sulphate.. . . . . Manganese dioxide. . . . . . . Manganese sesquioxide.. . . Manganese sulphide.. . . . . . . . . . . . . .4d, 6d, 10d Manganous pyrophwphate . . .4ch, gh, 6ch, ~ o c h Manganous sulphate.. . . . . . . . . .! . . . I Mercuric oxide.. . . . . . . . . . . . . . . . . ..6, IO Mercuric s Mercurous Mercurous Mercurous . . . . . . . . . . . . . .6 Metastannic a c i d . . . . . . . . . . . . . . . . .. I O , 13
Kickelous hydroxide.. . . . . . . . . . . . . . ~cd, 14,23, 24,36 NickelousIsubsulphide . . . . . . . . . . . ..6
1211, 1311, 1411
932
GENERAL, PH’t’SICAL A N D INORGANIC. P t ecipitates.
Solvents.
Nickelous rulphidc . . . . . . . . . . (1 P;ilIndiiin~iodide. . . . . . . . . . . . . . . I.+ Platinum sulpl~ide.. . . . . . . . . . . . . . if),I S 1’ot;issiuiii cliloi-irle . . . . . . . . . . . . . I 11 I’otas4iitil col~alticnitrite . . . . . . . i l l Potassium I1uolx)r:ite. . . . . . . . . . .I , i t 1 P ~ ~ t a s s i ~clilr~rpl:~tir~atc irii . . . . . . . . 111, i i l i I’otassiuni sulp1i;itc. . . . . . . . . I 11 Silica. . . . . . . . . . . . . . . . . . . . . I I , 1rl1, 1~111,~ ~ ~juli, 1 1 ,~;-ignititrti Silver. . . . . . . . . . . . . . . . . . . . .f d Silver cliloride . . . . . . . . . . . . . . 1411 . Silver cyanide.. . . . . . . . . . . . . . .14, 4(J Silver iodide. . . . . . . . . . . . . . . . . . . .++c, . 2 2 , 40, 44ch Silver p l i o s p h a k . . . . . . . . . . . . . h , 14 Silver siilpliide. . . . . . . . . . . . . .Och-1-3 Sodiurn carbonate. . . . . . . . . . . . . . .i l l Sodiuni chloride. . . . . . . . . . .I 11 Sodium chlorplatiriate . . . . . . . . 111, z Sodium sulphate . . . . . . . . . . . .i h Stannic acid. . . . . . . . . . . . . . . . .1 0 - 1 Stannic oxide. . . . . . . . . . . . . . . . . . . ,$dry-ignition, . 10-1 Stannic phosphate. . . . . . . . . . . . . I 2 Stannic sulphide (hydrous). . . . . . . . .iocli, 1 2 , 15, I 7 Stannous sulphide (hydrous). . . . . . . i o c Strontium carbonate . . . . . . . . . . . . 7. , 24, $J Strontium sulphate. . . . . . . . . . ..*. . ~ 3 c ,3jc, , 38c, 3yc 1:r:myl pyroarsenate. . . . . . . . . 0 Uranyl pyrophosphate. . . . . . . . . . .4, 6, I O Zinc o x i d e . . . . . . . . . . . . . . .: . . . . . . Iodh Zinc sulphide.. . . . . . . . . . . . . . . . . . 1,6 . I O
A hlunroe crucible may be readily prepared by igniting a carefully dried layer of ammonium chlorplatinate deposited over the bottom of a perforated platinum crucible in the form of an alcoholic sludge which is poured into the crucible while the latter is pressed upon a n absorbent support to remove the excess of alcohol. The salt should be shaped during ignition, and lightly burnished thereafter, with a glass rod of suitable shape. If a felt retains cold, freshly precipitated calcium oxalate, it may be considered free from cracks and sufficiently fine to hold the finest precipitates. In case imperfections develop in the felt, by reason of careless or improper use, it may be readily restored to prime condition by saturating it with hydrochlorplatinic acid solution, allowing a moderately strong aqueous solution of ammonium chloride to diffuse upwards throughout the felt by loxi-ering the crucible slowly into a beaker containing the ammonium chloride solution. washing with alcohol, drying, and igniting.
