Skeleton notes on analytical chemistry : for students in medicine / by Albert J. Bernays.

  • Albert Bernays
Date:
1879
Catalogue details

Licence: Public Domain Mark

Credit: Skeleton notes on analytical chemistry : for students in medicine / by Albert J. Bernays. Source: Wellcome Collection.

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    Ca and Mg may also be precipitated by NH^II; therefore the orifriual substance must he tested on Platinum with H.SOj,— a BORATE gives green color to flame. Fluorides evolve HF, whicli corrodes gla.ss. If either present, add more NH^Cl and test for Ba, Sr, Ca or Mg. If insoluble in HCl, boil with HNO3. Kemove nearly all the free acid by evaporation, and test the solution for tlie various bases under the different Groups. If insoluble in HNO3, boil with aqua regia. Remove free acids, dilute and tost. Be careful to remove both HNO3 and Cl^, as they decompose HjS, with deposition of Sulj^hur. As regards tlie examination for the radicle in substances only soluble in acids, indications have already been noted (p. 40). All borates are soluble in HCl; on Platinum with HoSO^. all borates give green color to flame. In the HCl solution, BaClj discovers a sulphate (p. 35); in any sulphide, the action of nitric acid would be to create a sulphate. In the case of silicates, evaj^orate to dryness, ignite and re-dissolve in HCl : silica SiOj, remains undissolved. Phosphates are all decomposed by acids ; their detection has been explained at pp. 36, 41. In the case of an organic salt, blackening with a residue would occur; dissolve the residue in HNO3, evaporate, re-dissolve in water, precipitate by HjS or by ]Sa2C03, and in the filtrate test for the base. If a SVBSTANCE is insoluble in water as W^ELL as in ACIDS, various methods must be employed. Carbon disajipears wiien strongly ignited, and deflagrates with KNO3. AgCl, AgBr and Agl melt when heated, and give metallic Ag, heated witli NajCOg. ALO3, is white, infusible, is turned blue, when ignited with Co'iNOj.- unlocked by fu.sion with KHSO^. SnO, and Sb^Oj give ductile or brittle metallic bends respectively of Sn or Sb when heated on charcoal with Na2C03. In a platinum capsule they may be reduced by Zn + HCl; Sb will stain the Pt black. They may also be unlocked by fusion with Na^COj. Silica and certain silicates are untouched by acids; heated in the sodium metaphosphate bead they yield a skeleton of B\0„. They can be unlocked by HP; or by fusion with Ba(0H)2; or with 3 times their weight of Nn2C03, treatment with HCl, evaporation to dryness, moistening with HCl, and addition of water which leaves SiOj undissolved. If K or Na to be sought for, then Ba(OH)o must be used. Fluorides are white : all evolve HF when heated with HoSOj, and corrode a watch-glass placed oyer the platinum caiDsule. Chromic oxide gives a green bead with borax, [t is best unlocked with a mixture of Na^COj and KNO3, yielding soluble yellow chromate. Some alloys are best heated
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