Practical organic and bio-chemistry / by R.H.A. Plimmer.

  • Robert Plimmer
Date:
1915
Catalogue details

Licence: Public Domain Mark

Credit: Practical organic and bio-chemistry / by R.H.A. Plimmer. Source: Wellcome Collection.

    565/660 page 545
    Of the various methods proposed for estimating small quantities of iron the best seems to be the titanium chloride method which depends upon the re- action :— TiC], +-FeCl, = TiCl, + FeCl, Jahn! has worked out the details for its use with physiological liquids and tissues :— (1) Zhe Preparation of a Standard [ron Solution. Instead of using ferrous ammonium sulphate it is more convenient to use pure ferric oxide (Kahlbaum). The oxide is heated at 150° for 5 hours to remove the last traces of water. 0'14297 gm. ( = *r gm. Fe) are placed ina round bottom flask and dissolved by heating in 20 c.c. of concentrated sulphuric acid and 200 c.c. of water. The flask 1s shaken on account of bumping, allowed to cool several times, and water lost by evaporation replaced. The clear solution is diluted to 1000 c.c. (1 c.c. = o’ooo1 gm. of Fe). (2) Preparation and Standardisation of the Tittantum Chloride Solution. ro cc. of commercial 15 per cent. titanium chloride solution are gently boiled in a very small beaker with 10 c.c. of pure concentrated hydrochloric acid. The vapours are tested for hydrogen sulphide with lead acetate paper, and if it be present the solution is boiled till it has been removed. The solu- _ tion is rapidly cooled and diluted in a flask to 2000 c.c. with boiled out water. Owing to its being so easily oxidised it must be kept in an atmosphere of hydrogen prepared in a Kipp apparatus and freed from hydrogen sulphide by passage through permanganate. The flask is therefore fitted with a rubber stopper with two holes; the tubes through the stopper pass to the bottom. Hydrogen is passed through one tube and the other tube is connected to a burette. The burette is also connected with the hydrogen apparatus. The titration must be carried out 1n an atmosphere free from oxygen and is effected most conveniently in a 250 c.c. filter flask, through which by the side tube a current of carbon dioxide is passed; the end of the burette should reach below the level of the side tube. to c.c. of the iron solution are placed in the flask and diluted with roo c.c. of air-free water. ‘10 c.c. of pure concentrated sulphuric acid are added ; when the solution is cold 5 c.c. of 40 per cent. potassium thiocyanate are added as indicator. When the air has been displaced by carbon dioxide the titanium solution is run in till it is colourless, i.e. in excess. The excess is determined by titrating with the iron solution until a red colour appears. This red colour must be permanent for 5 minutes, e.g. :— 10 C.c. iron solution + 7°75 c.c. titanium solution + 4°3 c.c. iron solution. 7°75 c.c. titanium solution = 143 c.c. iron solution = 14°3 mgm. iron. .. I¢.c, titanium solution = 0°1845 mgm. Fe. Owing to the instability of the titanium chloride solution it should be standardised before and after a series of iron estimations. (3) Estimation of Iron. 5 c.c. of concentrated sulphuric acid are added to a measured volume of the solution: when it is cold 5 c.c. of 40 per cent. potassium thiocyanate are added, the air is displaced and excess of titanium solution is run in. ‘The excess is determined by titrating with the iron solution, e.g. 20 ¢.c. titanium solution were used and excess titrated with 3°2 c.c. iron solution, 20 ¢.¢c. titanium solution = 3°690 mgm. Fe — 3°2 mgm. Fe = 3°370 mgm. Fe, 1 Z, physiol. Chem., 1911, 75, 308, a
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