Biochemical notes : laboratory work. First and second parts.

  • Gies, William John, 1872-1956.
Date:
1906
Catalogue details

Licence: Public Domain Mark

Credit: Biochemical notes : laboratory work. First and second parts. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    four and five that were contained in the original precipitate (15). It may also contain a trace of iron that was not precipitated in the foregoing process. A method for removing such a trace of iron is indicated below (24). Proceed to 24. 23. Fourth group. Of this group manganese is the only one of general biological significance. It can seldom be detected by ordinary means because of the slight proportions in which it oc- curs. Like iron it occurs mainly if not wholly in organic combi- nation. (See footnote, page 8.) 24. Mix filtrates 15 and 22. Reduce the volume one half by evaporation. Add to the concentrated liquid a moderate excess of ammonium hydroxid, and boil until nearly all ammonia has been eliminated. Filter, if any trace of iron, or anything else that had not been previously precipitated, should be thrown out of solution at this point. Add colorless ammonium sulfid, in slight excess. Heat to boiling. Filter if necessary.* Proceed to 26. 25. Fifth group. Of this group calcium is the only element of biological importance. It is a relatively prominent constituent of practically all organisms. 26. Calcium. The preceding filtrate (24) should be concen- trated by evaporation and cooled. Excess of ammonium sulfid is expelled in this process. If a precipitate forms as a result of this treatment add just enough water to dissolve the precipitate.f Render the liquid alkaline with ammonium hydroxid and add * As a rule precipitation does not occur because of the absence of manganese and the remaining metals of the fourth group or because only the merest traces are present. If a precipitate is produced, however, test for manganese as follows : Dissolve the precipitate on the filter in dilute hydrochloric acid. To the filtrate add excess of sodium hydroxid. If manganese was present it will be precipitated as white manganous hydroxid which will gradually be converted into the brown manganic hydroxid. Put the filter and precipitate in a casserole and heat to boiling in nitric acid. Add several very small quantities of red lead (less than half a gram in all). Boil again for a moment. Filter. A pink filtrate indicates the presence of manganese. This color must be looked for immediately after filtering. When only a small proportion of manganese is present the faint pink color speedily disappears as a result of oxidation. The color may usually be seen on permitting the excess of PbjO^ to subside. (L : 138.) Equation : 2Mn(0H)j + bVhf)^ + SOHNO, = 2HMnO, 4- 15Pb(NOs)2 + 16H.0 Permanganic acid (red) If manganese is present in the precipitate produced by ammonium sulfid, the precipitate will impart an amethyst-red color to a borax bead when it is heated with the latter on a platinum wire in an oxidizing flame. In a reducing flame the bead becomes colorless. t If sulfur s^'parates filter the mixture.