FLORENCE J.LCKSOK.
992
Amoillit K.0 added. Parts per-million
...... ........
Amount K 2 0 recovered Parts per millioti.
I..
1.0
0.92
2
1.0
0.
........ 1.0
3 4 ........ j
1.0
........ 2.0
........ 2 . 0 j... ..... 2 . 0 8 ........ 2 . 0 9 ........ 3.0 I O . . ...... 3.0 11 . . . . . . . 3.0 I2 ........ 3.0 13. ...... 4.0 14........ 4.0 r j ........ 4.0 16.. ...... 4.0 1 7 . . ...... 5.0 6
1s........ 19..
j.0
...... 5.0
......TO.O 21 ........
20..
10.0
S
I .O 1.2
1.9 2. I
2.0 2.0 3.2
3.2 2,s
2,s
4.4 4.0 4.0 4.4
5.0 5 .o 4.9 11.6 11.2
XEW HAMPSHIRE COLLEGE, AGRICULTCRAL
EXPERIMEST STSTIOS.
THE DELICACY OF TESTS EIIPLOYED FOR THE DETECTION OF IIETALS. BY FLORENCEJ A C K S O N Received J u n e Z P , 1903,
THEwork in the following paper mas undertaken for the purpose of determining the comparative delicacy of the tests employed in the ordinary methods used in qualitative analysis in detecting metals. To this end, solutions of salts were made of such strength that I cc. of the solution contained 5 mg. of the element under consideration or I part in 200. The weaker solutions were made from the standard bydiluting with distilled water. When (as in the case of silver chloride) ammonia present in the water might exert a solvent influence, water free from ammonia was used. The reagents used were of thestrength employed in the Wellesley College Chemical Laboratory (see table at the end), and were added drop by drop to I cc. of the solution under consideration. The experiments were carried through twice, new standard solu-
TESTS EMPLOYED FOR THE DETECTION O F METALS.
993
tions being used the second time and, in cases of discrepancy, further tests were made. The figures under the "final tests" were chosen as the probable limit of detection, if the element was not known to be present. They do not, therefore, usually represent the extreme limit indicated under the experimental conditions of this paper. This may account for the discrepancy between my figures and those giver1 by other authorities. FINAL TESTS.SUMMARY BY REAGENTS. ( A ) HC1. ( a ) SP. gi. 1.035
r~ : ~,ooo,ooo.Comey.
Mulder. 378,000. Harting. ~g 1 :649000{ 200,000. Lassaigne. I I : 18g,ooo. Pfaff. HgI I : 16,000 I : 3 2 7 , m . Fresenius. Pb I : 500 I : 1,077. Wormley. ( b ) Sp. gr. 1 . 1 As above except Hgl I : 8,000 ( B ) NaCI. Ag I : 3z.orio Hgl I : 15,000 Pb I : 1,000 (C) HZS. AsT' I : 1,024,000 I : 13,200. Wormley. Sb I : 51z,ooo I : 24,000. Wormley. Bi.Ag.SnlI I : 64,000 As.VHg.1 SnIV I : 32,000 As I : 1j30. Wormley. I : 1,000,ooo. Prescott and Sullivan. I : 2 6 , ~ .Wormley. Hg" I : 46,000. Green coloration LasI : 23,000. Brown " lsaigne. Cd.Cu.Pb.HglI I : 16,000 I : 6,770. Wormley. I : 1 0 0 , 0 0 0 . Prescott and Sullivan.
i
~
IPb
( D )",OH. Mn Mg Co.Fe.II' P b
I
: 64,000
I :32,000 I : 16,000
Al.Bi.Cu.Fe.llHg.l-llSn.llZn I : 8,000
HgI1 I : 13,500. Wormley. : 20,000. Prescott and Sullivan. I : 12,500. Wormley. Zn I : Iz,joo. Wormley. I
Cd.Cr.Ni.SnIV Sb Ag.(NH,OH I : IO)
I
: 4,000
I
: 1,000 : joo
I
I
: 1,200. Wormley.
991
F L O R E S C E JACKSON.
( E ) SaOH. a111
I
: 12S,OCO
Fell1 I : 32,000 . l l . C ~ . C o . H g .S~i I : 16,000 Cu I : 12j,000. Wormley. NH,Bi.Cr.Fe.llAg I : 8,000 Cd.h I : 4,000 Sn" I\' I : 2,000 Sh I : 1,000 I : 1,200. li'ornlley. Pb.Hg" I : j o o Hg'I I : 677. Wormley. ( F ) K2Cr04. Ba I : zj6,ooo (I : 111,gSz. Harting. Pb I : 32~00011 : 107,700. l\'ormley. Cu I : 16,000 I : jo,om. Wormley. A g I : 8,000 Bi.Hgl I : 4,000 Cd I : 1,003 Hg" I : 333 Sr I : zoo ( G ) KI. Ag I : 47,ZjO. Harting. Ag.Cu.Pb.Hgl I : S,oooi P b I : 21,540. Wormley. Cu I : 12,500. Wormley. Hg" I : 2,000 I : 3,380. Wormley. ( H ) Na,HPO,. hIg I : 1~8,000 (Addition of XH,C1 and ",OH.) Ca I : 16,000 Ag.Sr I : &om Ba I : 4,000 (I) (KH,)2S. Co I : jIz,ooo I : jog,ooo. Pfaff. FelI.II1 I : IZQ,OOO Xi I : 64,000 Al.Cr.Mn.Zn I : 8,000 (1) H,O. Sb I : 2,mo Bi I : 4,000 ( K ) Nn,CO,. Sr I : 64,000 Bi.Mn.Ag I : 32,000 Cu.Fe.I!l Hg.' S i I : 16,000 Cu I : 12,500. Wormley. Al.Ba.Co.Fe.lIZn I : 8,000 Zn I : 12,500. Wormley. Cd.Ca.Cr.Ph.Mg I : 4,000 P b I : j3,Sjo. Wormley. Hg" I : 250 (L) H,SO,. Ba I : 256,000 I : 79,300. Harting. Pb I : 16,000 I : 21,540. Wormley. Sr I : 8,000 I : 23,100-z5,z00. Fresenius. Ca I : 2,000 Hgl I : 1,000
TESTS EMPLOYED FOR THE DETECTION OF METALS.
(iM) SnCI,. I
: :
I
:
16,000
I
:
2,000
I :
1,000
Hgl HgI1
I
32,000
I :
16,000
13,500. Wormley.
( N )KCN. Co Cu.Ni Cd ( 0 ) K,Fe(CN),. Fell1 Fe.IrPb Cu
I
: 64,000 : 3 2 , 0 0 0 Pb
I
:
I
I :
10,770.
Wormley.
: IOO,OOO. Prescott and Sullivan. . I : .31,250. Wormley. I
16,000
( P ) ("4),COs. Sr I : 16,000 I : 95,200. Coniey. Ca.Co.Felll I : 8,000 Ca I : 163,000. Fresetiius. Ba.FelI I : 4,000 Ba I : 201,000. Fresetiius. Mg I : 200 ( 9 ) ("I)~CZO~. Ca I : 64.000 S r I : 32,000 Ba I : 2,000 ( R ) CaSO,. Ba I : 64,000 Sr I : 1,000 (S) H,SiF6. Ba I : 2,000 zoo K I : Na
:
143
I : I :
2,000
I
( T ) H,PtCI,. NH, K
200
REAGENTS EMPLOYED. (NH,),CO,. .175 grams to a liter $- 100 cc. concentrated ",OH. .............Diluted I : 3 and I : I O . ",OH.. (NH,),C,O, -4sgrams to a liter, Saturate ",OH (0.96) with H,S. (NH,),S HCI ..................Sp. gr. 1.12and 1.035. .Sp. gr. 1.2. HKO,. H,S04 ................Diluted I : 5. H,S. From Kipp generator. Washed in H,O. . 2 5 grams to a liter. HgCI,. MgSO,. ............... so " '/ " K,CrO, ................50 KCN. 50 " ii " KCNS ............... 5 " " " " " " 'I K,Fe(Cn), ............ I .? KI -'5 " ' I '' '' Na,CO, ..z50 Cry st a1lized salt. NaCl ..................50 NaOH .............. 150 I ' * ' ' I Na,HPO, 50 SnCl, Sn dissolved in HC1 f 4 parts of H,O. STRENGTH OF
.......... .......... .............. ............... .................. ............... .................
-................... ........... .............. .................
........
L '
.. .. .. .. .. .. .. .. ........ ' j
995
996
D.
MCINTOSH.
T h e results obtained from these experiments agree, in general, with facts already knon.n. The i ~ o r khas value chiefly, as it seems to me, in the collection of definite data for future investigation rather than in any new facts brought to light by the figures given. WELLESLEYCOLLEGE, June, 1903.
A LECTURE EXPERIMENT WITH AN UNDISSOCIATED SALT. BY D. MCINTOSH. Rece*ved lune 18,
1903
WHENa sulphocyanate is added to a ferric salt, the deep red color produced is thought, for a number of reasons, to be due t o the undissociated ferric sulphocyanate. These may be briefly stated: First, neither the ferric nor the sulphocyanate ion is colored ; second, the crystals of ferric sulphocyanate, which can contain no ions, are similarly colored; third, in ether, in which salts are but slightly dissociated, the color is unchanged; fourth, an excess of a sulphocyanate increases the color, while the addition of sulphate ions weakens it. If, then, ferric sulphocyanate were placed in a tube between two layers of a colorless iiquid, the passage of a current should not increase the rate of diffusion ; if, on the other hand, the color were due to a c m p l e x cation or anion, the color should move either to the cathode or anode. If a solution of ferric sulphocyanate be placed in a U-tube, and carefully covered over with a less dense electrolyte (dilute hydrochloric acid), a current of ampere may be passed through it for several hours without the relative positions of the colorboundaries changing. The experiment can be made quite striking, by arranging in series two other tubes containing1 potassium copper tartrate covered with dilute potassium hydroxide, and copper sulphate with ammonium hydroxide covered with ammonium hydroxide. In the first case, the color-boundaries remain stationary, while in the second and third they move towards the anode and ca!hode respectively. 1
Massoni: 2 f s c k r . p h y s . Chem., 19,501 (1899).
