Theoretical organic chemistry / by Julius B. Cohen.

  • Julius B. Cohen
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: Theoretical organic chemistry / by Julius B. Cohen. Source: Wellcome Collection.

    63/604 (page 43)
    is then weighed and ignited, and the metallic residue of silver weighed. If W is the weight of salt, w the weight of silver, and n the basicity of the acid, the molecular weight of the silver salt is determined from the following formula :— W x 108/z w The molecular weight of the acid is then obtained by deduct¬ ing n atoms of silver and adding n atoms of hydrogen. Example.—o'3652 gram silver salt of a monobasic acid gave o'172 gram silver. 108 x '3652 •1720 229-3. This represents the molecular weight of the silver salt. As it contains one atom of silver in place of one atom of hydrogen (being a monobasic acid), 108, the atomic weight of silver must be deducted and 1 added for the atom of hydrogen. M = 229'3 - 108 + 1 = 122*3. Molecular Weight of Organic Bases.—The organic bases (B) form, like ammonia, crystalline chloroplatinates with platinic chloride, of the general formula, B2H2,PtClc. By estimating the amount of platinum present in the salt, it is possible to calculate the molecular weight of the platinum compound, and, con¬ sequently, that of the base. The base is dissolved in a slight excess of moderately strong hydrochloric acid, and platinic chloride added. The chloroplatinate is precipitated as a yellow, crystalline powder resembling the ammonium salt, and is care¬ fully washed and dried. A portion is then weighed and ignited in a crucible and weighed again. The molecular weight of the salt is calculated from the weight w of the platinum and W of the salt, according to the formula (the atomic weight of platinum being 195)— W x 195 w To determine from this the weight of the base, it is necessary to deduct from the molecular weight of the salt that of H2PtClG, and as 2 molecules of the base are contained in the salt, the result is halved.