314
LOUIS RAHLENBERG.
ON THE SPEED OF
466.850 480.052
5.763
1.61
1.53
5.960 ;.98
455.00 471.375
345.23 352.033
2,332 1
436.165 458.275
346.325 381.875
1.958
j
0.51
427.580 652.350
346.435 471.920
1.690
,
048
6.2
354,200
346.250 4;1.22.5
2.495
346.465 352 435
1.585 3 99
643.320
346.320 614.920 342.300
602.365
340 500 600565
328.84 567.62
317.83 555.365
2 19,450
210.765 543.165
1.709
1.985
2
9 225 IO 165
592'200
327.140 581.465
557.165
I4 355
333 075
594.m
334.875
5.82
'
~
,
I535
Average percentage loss..
..
0.57
52
,*
~
, I 3.465 I
54 per cent
1.29
0 0 4s
~
2.385 3.705
.2
49
I I1
73
2.9s
...
0
0.4j
2.25
Average percentage loss..
0.60
0
1.71
7 735
2.10
0
~
~
0.44
0.63 0.9 0.83 1.07 1.05
87 per cent.
__
.. - ._
RENSSELAER POLYTECHNIC INSTITUTE,
1893
ON THE SPEED OF REDUCTION OF FERRIC CHLORIDE BY STANNOUS CHLORIDE. Bs I,OCIS KAHLENEERG. Keceived February 8 , ,894.
T
HE reaction that takes place when ferric chloride is treated
with stannous chloride in aqueous solution is expressed by the following equation : Fe,Cl, SnCI, = 2FeC1, f SnC1,. This reaction goes on slowly enough at ordinary temperatures to admit of study from the standpoint of chemical dynamics. It was my purpose to investigate whether the reaction proceeds
+
3x5
R E D U C T I O N OF F X R R I C C H L O R I D E .
in accordance with the law of mass action, as stated by Guldberg and Waage,' and how the speed of the reaction is affected by the presence of varying quantities of free hydrochloric acid. Outline of Method of Exjerintenfation.-Solutions of ferric chloride and stannous chloride of known strength were prepared. These were brought to a definite temperature by allowing them to stand in a bath. They were then quickly mixed (in equivalent proportions), and the mixture was kept at the same temperature in an atmosphere of carbon dioxide. At convenient times, samples were taken out'with a pipette ; these were quickly run into an excess of a saturated solution of mercuric chloride, which, by converting the unchanged stannous chloride into stannic chloride, according to the equation, SnC1, 2HgC1, = SnC1, 2HgC1, checked the reaction. The amount of ferrous chloride formed was then determined by means of a standard solution of potassium bichromate. I n this process, the bichromate was added until a drop of the mixture on a white porcelain plate showed no longer a blue coloration when brought into contact with a drop of a dilute, freshly prepared solution of potassium ferricyanide. Preparation of Solutions.-A decinormal solution of potassium bichromate was prepared by taking 4.913grams of the pure salt to a liter. Its strength was verified by comparison with both ferrous ammonium sulphate and iron wire. 17.85 cc. of this solution will change 0.1gram of iron from the ferrous to the ferric state. The ferric chloride used was of Merck's manufacture (C. P.). It was tested for arsenic and for sulphuric, nitric, and free hydrochloric acid, and found pure. Four liters of ferric chloride solution were prepared. T h e strength of this solution was determined by means of the decinormal bichromate solution, after previous reduction at a boiling heat with a slight excess of stannous chloride, and addition of an excess of mercuric chloride before titrating.' It was found that twenty-five cc. of the ferric chloride solution were equivalent to twenty-eight cc. of the bichromate. 1 Etudes sur les affinites chimiques. IO,Christiania, 1867; also]. )vuRf. Cheni., [PI, 1g,6g.
+
2
Kessler, h g g . A n n . . 95, 223-225; also Zfscht. anal. Chem., 1 1 , 249.
+
310,
I,OL.IS I. lioiletl, \\-as added froiii tiiue to time so as to keep the d u ~ i i of e the liquid at about IOO cc. \Then the cheniical action lint1 ceased, about four to five granis of tin still reniaiiied unclissol\-txl. T h e excess of hydrochloric acid was driyeii off by 1)oiliiig the liquitl down to a siiiall h l k . T h e stannous chloride thus ohtained was diluted to 4,000 cc. with \\-ater previously boiled antl cooled i i i a11 atriiospliei-e of carboii dioxide. That the free h!-drochloric acid had been driven off \vas evident from the fact that a precipitate of stannous oxychloride formed b y diluting to t!iis volunie. It rvas found necessary to add, to the four liters t\veiity cc. of lijdrochloric acid, of sp. gr. I . I 7 %to bring this precipitate into solution. .\iter this addition of acid and thorough slizkiiig there still I-eiiiaiiietl ;i fairit opalescence. sliowitig that a iiiiriiiiiuiii quaiitity of acid had bee11 used. The solutio11 thus prepared was at o~icetransferred to a number of flasks holding from 2 2 j t ( J Z
