NEW ORGANIC QUALITATIVE REAGENTS J. W. SMITH
H. E. ROGERS
AND
Dickinson College, Carlisle, Pennsylvania
This paper is the result of a search for some new organic istic pink solution for dilutions as low as 0.001 gm. Sb/ml. qualitative reagents. Mercurous mercury, silver, lead, of solution. Stannous tin decolorizes Bordeaun Red antimony(ow), tin(ous), calcium, barium, and strontium completely. Antimony(ous) and stannic tin do not. mere precipyated in 0 a r i u s forms i n the preselece of four- Calcium, firecififukd as hydro&e, i n the presence teen water-soluble dyes. Silver precifitated as sulfate, of Brilliant Yellow, gives a pink precipitate. Barium and gives a characteristic test, with Brilliant Yellow used. If strontium, under the same conditions give orange-colored Bordeaux Red i s employed antimony (ous)givesa character- precip'tates and solutions.
T
HIS paper presents the results of some experimental work carried on by one of the authors in connection with a senior honors course in the department of chemistry. Experimental work, upon which this paper is based, TABLE 1 Sn,"mt (As+)
~ e s u 1 ojw 1 Pal. with 4 N Sodivnr CorD% NO.
9
12
Ashen-gray ppt. Yellow-gray ppt.
Rerull ojter POI. wilh 1 N
-
Pink ppt. MBRCWOUSMBRCUIY (HE+)
Dye No. 1 2 3 4
5 6
7 8 11 14
Rcrulr ofln POL wilh 4 N Sodivtn Resull oflsr Pel. with 1 N Carbnorr H~SOI Dark green ppt. Yellow-brown ppt. Dark ween ppt. Dark g r e ~ nppt. Dark green ppt. ~ i g h pink t ppt. Dark green ppt. ark green ppf. Light yellow ppt. Pink ppt. Gray ppt.
-
-
(~b++)
..".
nu, M. -,"
ojin POI. will 4 N Sodium cn.hmmn,.
1 3 7
Piak ppt. -
8
Cream ppt.
R e W l o f r e POI. d l h a.w.
-
~ l u e - g r a yppt.
-
has had for its object the search for some new organic qualitative reagents. From the dyes available in the stock room, fourteen of those soluble in water were chosen. They were (1) Bordeaux Red, (2) Brilliant Violet, (3) Brilliant Yellow, (4) Brilliant Green, (5) Phloxine, (6) Pyronin, (7) Phenosafranin, (8) Fluores-
cein, (9) Alizarin Red S, (10) Naphthol Yellow, (11) EIythrosin, (12) Ponceau 2 R, (13) Bismark Brown B, and (14) Hoffman Violet 3 R. The metals chosen for investigation were mercurous mercury, silver, lead, antimony(ous), tin(ous), calcium, barium, and strontium. Salts of the above metals were placed in solution (0.01 gm. metal per ml. of solution). Into successive test-tubes, five to seven ml. of the salt solution were introduced. From a dropping bottle, two or three drops of the aqueous solution of the dye were introduced. By means of a 10-ml. pipet, a sufficient amount of reagent capable of precipitating the metallic ion was now added to each test-tube. Precipitating reagents were 1 N sulfuric acid, 6 N potassium hydroxide, 5 N ammonium hydroxide and 4 N sodium carbonate. Upon the precipitation of the metal, the precipitate was examined carefully in order to determine if i t had taken on a new and distinct color or if the dye solution itself had changed color. The following results were obtained. A dash in the following tables indicates there was no change in the color of the dye or the precipitate. The one test in this group, which is considered characteristic, is the precipitation of silver from a nitrate solution, containincc three drops of an aqueous solution of ~ r i l l i kyellow: t The silver was precipitated as sulfatewith dilute HeSO4. The silver sulfate which settled out was definitely burnt orange in color. Due to the fact that silver sulfate is not verv insoluble. this test cannot be applied to silver solutions of low concentration. The detection of antimony in the presence of tin, using the usual. platinum-tin couple or the tin-zinc couple is quite unsatisfactory. It has been our experience here that students report antimony incorrectly very frequently, as a result of this confirmatory test. It was with this in mind that antimony(ons) and
143
tin(ous) were precipitated in the presence of the above dyes. Antimony trichloride was dissolved in a hydrochloric acid solution. The dye was added as described above in the case of the Group I metals. The antimony was then precipitated with ammonium hydroxide with the following results. TABLE
a
Arnlao~u(0"S) (Sbf++)
Dye
No. 1 3 7
13 14
In connection with this test i t was noted that hydrochloric acid solutions of antimony(ous) and stannic tin had no effect on the color of the dye. On the other hand, stannous tin decolorized the Brilliant Red as soon as it was added. This suggests the possibility of using Brilliant Red to distinguish between antimony(ous) and tin(ous) and also between stannous tin and stannic tin. In investigating the effect of the dyes on calcium, strontium, and barium the following results were obtained:
Rerult on Addilion of 5 N NH'OB Ught pink ppt. and pinkrolrrtion Flesh ppt. fight purple ppt. mesh ppt. Pale blue ppt.
The same procedure was employed, stannous chloride substituted for antimony trichloride with the following results.
TABLE 4 B*Xm,M
(Bat+)
Dre No. 3 4 8
-
Very light orange ppt.
-
Pink ppt. Purple ppt.
c*,.crou (Cat+)
TABLE 3 ~N((JVS)
Resxli on Addition o f 4 N SnZium Rcsult on Addition of 6 N KOH Carbonate
3 9
orange ppt.
Pink ppt.
-
P w l e ppt.
(Sn +) +
Dve No.
10 14
Rcrdr oflrr Addilion of 5 N NKaOR White ppt. and colorless solution Pale blue ppt. Liehf blue not. .. ~ i . kppt. Light blue ppt.
If Bordeaux Red (Dye 1) is employed, antimony may be detected in the presence of tin. Antimony, alone, gave a characteristic pink solution for dilutions as low as 0.001 gm. Sb per ml. of solution. Tin gave a white precipitate under varying conditions of concentration. If the amount of tin present is not in excess of th'e amount of antimony, the pink-colored solution persists and thereby indicates the presence of antimony.
Sra0NllU~
(Sr*')
3
9
orange ppt. Purple ppt.
Orangeppt. and orange solution
-
In this group of metals one test appears to show possibilities. Calcium precipitated as the hydroxide in the presence of Brilliant Yellow (Dye 3) gave a pink precipitate. Strontium and barium, under the same conditions, gave an orange solution and orange precipitate. These tests were obtained when the concentration of the metal ion was 0.01 gm. per ml. When the concentration was less than this the results were not so satisfactory.
