A manual of practical hygiene : prepared especially for use in the medical service of the Army / by Edmund A. Parkes.

Date:
1864
Catalogue details

Licence: Public Domain Mark

Credit: A manual of practical hygiene : prepared especially for use in the medical service of the Army / by Edmund A. Parkes. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    oiily 2 graius per gallon of carbonate of lime can remain in solution after boil- ing, a large precipitate will show that sulphate or chloride of lime is present. 4. Magnesia.—Filter the water from the oxalate of lime thrown down in 3, evaporate to a very small bulk, filter again if there be any precipitate, and add a few drops of chloride of ammonia and phosphate of soda, and a few drops of ammonia. In tAventy-four hours, if magnesia be present, crystals of anmioniaco-magnesian phosphate are thrown down. 5. Potash and Soda.—It is not often necessary to examine this point, but if it is wished to do so, the process is as follows :—Take a portion of the liquid from which lime has been thrown down ; evaporate to dryness, ignite gently to drive off ammonia; if magnesia is present, it must be removed as follows : Add baryta water,,boil, filter; add to filtrate carbonate of ammonia and some caustic anunoniaj evaporate to dryness, adding some chloride of ammonia diu'ing the process; evaporate, ignite; then dissolve in a little water, and divide into two portions. (a.) Test one portion with bichloride of platinum for potassa. (&.) Test the other with antimonate of potassa for soda. As this process is complex, and as potash is seldom present in large amount in drinking water, it will be generally sufficient to evaporate the water at once, and see if it is alkaline ; if it is not, we may be sure no great amount of car- bonate of soda is present. 6. Chlorine.—Add a few drops of dilute nitric acid, and then nitrate of silver. Four grains per gallon of chloride of sodium give a turbidity; 10 grains, a slight precipitate ; 20 grains, a considerable precipitate. A guess can thus be made at the amount. 7. SidjJhuric Acid.—-Add a few drops of dilute hydrochloric acid, and then a few drops of chloride of barium. If no precipitate occurs, let it stand for twenty-four hours. Sulphates to the amount of 1, or even grains per gallon give no precipitate; at first, or even on standing, 3 graius give a haze, and after a time, a slight precipitate; above this amount, the precipitate is pretty well marked. If there is no precipitate, the presence of sulphates in small amount (1 to 2 grains per gallon) is not excluded. 8. Phosjihoric acid, by adding a little nitric acid, and then an excess of molybdate of ammonia, and boiling. If PO^ is present, a yellow colour, and in. time a finely powdered yeUow precipitate of phosphoric molybdate of ammonia falls, or a salt of magnesia, and liquor ammonia3 may be added to throw down the ammoniaco-magnesian phosphate ; or add a very little dilute nitric acid, and an excess of acetate of soda, and then a drop of sesquichloride of iron; a yeUow-white flocculent precipitate falls. As phosphoric acid is in small amount, the water must be concentrated. 9. Test for nitric acid, by evaporating a pint to a very small bidk ; put in a test tiibe; add an equal bulk of 2)ure sulphuric acid,* so that it may form a layer under the water; allow to cool; and then drop in a crystal of sulphate of iron. A dark olive-green or brown ring wUl form at the junction of the two liquids if nitric acid be present. Or after the water has been greatly concentrated, add a little sulphuric acid and a drop or two of sulphuric acid and indigo, and warm; the blue colour wUl disappear if nitric acid be present. Two tests have been lately proposed, which are perhaps still more delicate : Brucine Tes^.—Dissolve 1 part of brucinc in 1000 C.C. of distilled water. * The suliihuric acid mav be tested by brucine for nitrous acid, or by adding a particle ol bichromate of rta.sh ; if nitrous acid be present, the green oxide of rhronnim is (ornied.