The chemical examination of water, sewage, foods, and other substances : by J. E. Purvis and T. R. Hodgson.

  • Purvis, John Edward.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The chemical examination of water, sewage, foods, and other substances : by J. E. Purvis and T. R. Hodgson. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    The nitrogen in organic combination (as urea, uric acid, indol, skatol, and other proteid substances) is oxidised by the action of the alkaline solution of permanganate to ammonia. The amount of ammonia obtained is, therefore, a measure of the organically combined nitrogen present in the sample. Estimation of total solid matter. Measure out lOO c.c. of the sample into a weighed platinum dish, and evaporate it to dryness on a water bath; then place the dish in a water oven at ioo° C. for three hours; cool in a desiccator and weigh ; the increase in weight represents the total solid matter in icq c.c. of the water. Each mgm (=0-001 of a gram) of solid matter represents one part per 100,000. Chlorine as chlorides. Solutions required: Silver nitrate solution. Weigh out 2*4 grams of pure dry silver nitrate, and dissolve it in distilled water and make up to 1000 c.c. I c.c. of this solution = 0*0005 gram of chlorine; or when working on 50 c.c. i c.c. = i part of chlorine per 100,000. Potassium chromate solution. Weigh out 10 grams of potassium chromate, free from chloride, and dissolve it in 100 c.c. of distilled water. Estimation of chlorine as chlorides. Place 50 c.c. of water in a porcelain dish; add three drops of the potassium chromate solution, and run in the silver nitrate solution from a burette, with constant stirring, until a slight but permanent red brown colour is obtained ; then read off the number of c.c. of silver nitrate solution used. The silver nitrate precipitates the chlorine present in the water, as silver chloride ; and, as soon as all the chloride is precipitated, a reddish insoluble compound of silver chromate is formed. Oxygen absorbed from potassium permanganate solution. (i) Solutions required: ^ Potassium permanganate solution. Weigh out 0'395 gram of pure potassium permanganate ; dissolve it in distilled water