c. of acetic acid, adding the iodide, and proceeding
as before.
Substance Added. "Hypo" Required,
- 20. c.c
0.050 gram arsenic as As_{2}O_{5} 20.0 "
0.050 " antimony as SbCl_{5} 19.8 "
0.050 " lead as Pb(NO_{3})_{2} 20.1 "
A similar experiment with 0.050 gram of bismuth nitrate could not be
determined, the end-reaction being masked. Bismuth iodide is soluble in
potassic iodide, forming a brown solution, the colour of which is very
similar to that produced by iodine; and although it does not strike a
blue colour with starch, "hypo" has an action on it.
A similar experiment with 0.050 gram of iron as ferric chloride required
22.3 c.c. of "hypo," and the colour returned on standing. This shows
that ferric acetate liberates iodine under the conditions of the assay.
Trying to counteract this, by adding to a similar solution 0.5 gram of
phosphate of soda dissolved in a little water, 19.7 c.c. of "hypo" were
required instead of 20.0, but the assay showed signs of returning
colour.
In standardising, the same result was obtained, whether the copper was
present as nitrate or sulphate before neutralising.
~Effect of Varying Copper.~--With the same conditions as before, but
with varying amounts of copper and a proportionally increasing quantity
of iodide, the results were:--
Copper present 1.
Pages:
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384