31. The Determination of Copper and Iron in Dairy Products

Abstract

1. Two colorimetric methods for determination of copper have been described, viz. the xanthate and the sodium diethyl-dithio-carbamate. Both methods have given satisfactory results but the carbamate method has proved to be more sensitive and less liable to error from possible contamination than the xanthate method.2. The colorimetric determination of iron by the modification of the ferric thiocyanate method has been proved to give a very high degree of accuracy and excellent results have been obtained.3. A method of wet ashing has been described whereby organic matter is oxidised by the use of concentrated sulphuric acid and sodium nitrate and copper and iron extracted from the fat.4. A number of results are given showing the amount of copper and iron contamination that the cream is subjected to during the course of butter manufacture, and the distribution of copper and iron in the cream, butter and buttermilk.

Importance of Copper in Certain Color Changes in Butter

“…With butter, the following modification of the wet-digestion method described by Williams (1931) was used: Fifty grams of butter was weighed into a 250-ml. beaker and 15 ml.…”

A determinação do cobre pelo método calorimétrico do dietilditiocarbamato de sódio

“…WILLIAMS (1931) verificou que em amostras contendo pe quenas quantidades de cobre, o composto formado poderia ser extraído por solvente orgánico, aumentando a sensibilidade do mé-todo. 0 composto marrom amarelado, formado pela reação do cobre com o DDC, foi estudado por Dubsky (1940), segundo citação de WELCHER (1948).…”

Determination of minute amounts of copper in milk

“…Much of the copper was leached out of the paper by treatment with dilute copper-free hydrochloric acid, the amounts ranging from 0.00137 to 0.0051 mg. in the same series of papers. Williams (47) recommended treating the filter paper with copper-free hydrochloric acid for 24 hours, but the authors found that even such a treatment did not free it from interfering amounts of copper.…”