On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet.

  • William Marcet
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet. Source: Wellcome Collection.

    45/236 (page 25)
    case of flour, i. e., the bread may be kneaded in water, the fluid filtered, the clear filtrate mixed with ammonia and chloride of ammonium, and boiled; if a precipi- tate appear, the presence of alum is probable; let the precipitate be now collected on a filter, dried, moistened with a solution of nitrate of cobalt, and then burnt with the blowpipe flame; the appearance of a blue colour will be a satisfactory proof of the presence of alum. For a quanti- tative determination, ascertain the quantity of water present in the bread by desiccation, incinerate the dry mass, and digest it with dilute hydrochloric acid; then add ammonia, and apply heat to the mixture for some time, when the alum is precipitated in the form of alumina, which is collected on a filter, dried, and weighed. Hards and stuff.—Some bakers buy rock alum in pow- der, and mix it up in certain proportions with salt, the majority, however, make use of an article known in the trade as hards and stuff, consisting of a mixture of alum and salt. The method for detecting alum and determining its quantity has already been described; in regard to common salt, or chloride of sodium, its amount may be obtained by dis- solving in water the ashes of a weighed quantity of bread, and adding nitrate of silver and nitric acid to the filtered fluid, until no further precipitate be occasioned; the precipitate, which consists of chloride of silver, being collected on a filter, dried, and weighed, shows by a simple calculation the quantity of chlorine present corresponding to the chloride of sodium.^ Sulphate of copper.—This adulteration has not yet been detected in English bread; it is employed on the 1 100 parts of chlo--j „ 100 parts of chlo--v ride of silver con-] S^!^'^. • ^^'^^ ride of sodium^ ^^^^^^ • ^^'^^ tain ) Chlorine 2472 ^^^^^.^ J Chlorine 60-37 ■1 100-00 100-00