Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays.

  • Albert Bernays
Date:
1889
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Licence: Public Domain Mark

Credit: Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    130/182 (page 118)
    1. For Basyls of Groups I. and II. Dissolve in HC1, pass H._,S gas, boil, filter, evaporate off the H2S, neutralize carefully with KOH. 2. For other Groups. Dissolve in HC1, boil the solution with Na2COs in very slight excess, filter, neutralize the filtrate with HC1 or HN03. (Z>o not test afterivards for the acid employed.) These, in the subsequent paragraphs, are called the prepared solutions. N.B. Volatile acids (Group A) will be evolved on first treating ■with HC1. To test for Chloride in the original, a separate portion must be dissolved in HN03, AgNOs added, and the silver ppt. washed and tested as usual, Group-test A. HC1, added to the original and warmed, will liberate the volatile acids. Test the evolved vapors as follows: 1. Effervescence with no marked odor; Carbonate. Close the tube with the thumb to collect the gas, and decant it into lime- water in another test-tube. A white ppt. is CaC03, possibly with some CaS03. Add HN03 in excess, boil, add Ba(N03)2; if sulphite, a white ppt. of BaS04. 2. Odor of burning brimstone, besides the above test; Sulphite. 3. Odor of rotten eggs, blackening lead paper; the gas decanted into lime-water gives no ppt., but the solution, boiled with HN03, on addition of BaCl2 yields by oxydation a white ppt. of BaS04- With HC1 there may be a deposit of whitish Sulphur. Sulphide. 4. Bed fumes in the cold, bluing paper dipped in KI and starch paste. Nitrite. 5. A glass rod dipped in AgN03 is clouded white, and a smell of HCN may be noticed. Cyanide (also many ferro- ferri- and sulpho- cyanides). If sulphide be also present, apply the sulpho-cyanate test (p. 51). 6. Smell of S02, and deposit of S. Thiosulphate. The other tests (p. 40) give indications also in mixtures. [These acids may be isolated if necessary by distilling with dilute sulphuric acid, collecting the vapor in water, and neutralizing with KOH. In this case HF will also pass over, and will corrode the glass; acetic acid will be de- tected by odor and by Fe2Cl0 in the neutralized distillate; ferro- and ferri- cyanides will give HCN. Many organic compounds will decompose the H2S04, and give S02 if the distillation be carried too far.] 7. Chloric and hypochlorous acids will give off chlorinous vapors as in a simple salt. 8. Urates, and some others, will give with HCl a ppt. of the acid, which can be filtered off and specially tested. Uric acid chars on platinum with odor of burnt feathers; gives the Hurexide test, p. 54. See also page 73.