Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    96/272 (page 78)
    of the precipitate produced by the general reagent must be examined for chromium in the way described in the next paragraph. ‘To the filtrate from the chromium precipitate, or to the solution which has failed to give a precipitate, add hydrochloric acid until the solution is acid; then add one gram of chlorate of potash, and warm the solution so as to destroy all organic matter (note 2, page 80) ; add, lastly, ammonia in excess. ALUMINA, if present,* will be thrown down (L. 2. & 3.) as a white flocculent precipitate, on gently warming the solution; when a precipitate is pro- duced, it must be examined for alumina by the blowpipe test. When iron is present, the original solution must be examined to ascertain in what state of oxidation it exists; for this purpose a portion of the original solution must be examined for PROTOXIDE by means of ferricyanide of potas- stwm (202); another portion must be examined for the SESQUIOXIDE by means of the ferrocyanide of potassium (205). 192. 3d. Mix the rest of the washed precipitate with one part of carbonate of soda and three parts of nitrate of potash ; fuse the mixture in a porcelain crucible ; after the fusion, allow the mass to cool, and then boil it with water, and filter. If the filtrate has a yellow colowr, spsqutoxIpE OF CHROMIUM is present; confirm its presence by acidify- ing the filtrate with nitric acid, if chromium be present the solution will change, when acidified, to an orange red. If chromium is present, and it was not precipitated on boiling the alkaline solution (see 191), and a precipitate * If chromium has been found to be present in the way described in paragraph 192, and it was not precipitated from the alkaline solution (paragraph 191), it will, most probably, be precipitated by ammonia, the alumina reagent; it is necessary, therefore, to look for alumina in the way described in paragraph 192, when chromium is present and is not precipitated on boiling the fixed alkaline solution.