Bread-analysis : a practical treatise on the examination of flour and bread / by J. Alfred Wanklyn and W.J. Cooper.

  • Cooper W. J. (William John)
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Bread-analysis : a practical treatise on the examination of flour and bread / by J. Alfred Wanklyn and W.J. Cooper. 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.

    44/96 (page 32)
    In practice this method does not answer well, since the comparatively large gelatinous precipitate of mixed phosphates of lime and magnesia retains the phosphate of alumina with great obstinacy, so that it is well-nigh impossible to make a satisfactory determination of alum by the method. The method which is now adopted, and which is satisfactory, is founded on the difference in behaviour of phosphate of alumina and phosphates of lime and magnesia towards acetic acid. Whilst phosphate of lime and phosphate of magnesia dissolve with great readiness in acetic acid, phosphate of alumina is nearly absolutely insoluble in acetic acid. When the analyst has a mixture of these phosphates, such as is ob- tained in the course of an analysis of brc^ad-ash, he may treat it with acetic acid which will dissolve the phosphate of lime and phosphate of magnesia and leave the phosphate of almn- ina insoluble. The following are the details of the testing for alum, as carried out in our laboratory. 50 grammes of flour or 100 grammes of bread are placed in a platinum dish and ignited over a large Bunsen burner for several hours. This dish which avg are in the habit of using is tolerably stout and weighs about 100 grammes, its capacity when quite full up to the very brim l3eing200 cubic centims. Before being used the dish is polished with charcoal and weighed with accuracy. During the ignition the Bunsen burner is supplied with an excess of air, so that the dish may be as little as possible attacked by the gas : the ignition is moreover, manag- ed at a moderate temperature. The ignition is continued until the flour-ash docs not exceed one gramme in weight, and the bread-ash two grammes.