Soap content of some commercially refined oils; Effect of soap on the bleachability of the oils

Summary Samples of commercially refined cottonseed and soybean oils, from various points in the centrifugal sodium hydroxide refining process, were analyzed for residual soap content. The results indicate that the soap content of refined cottonseed oil, as it comes from the first stage of centrifugal separation, may vary anywhere from 0.038% to 0.672%. Soybean oil seems to be somewhat more consistent, running 0.183% to 0.207%. A single stage of waterwashing reduced the soap content of these oils to 0.03% or less and bleaching in the laboratory further reduced this concentration to below 0.005%. Of the two samples of commercially bleached oil examined, one contained 0.004% soap and the other 0.008%. Treatment on a plant seale with a filter aid only, followed by filtration, reduced the soap content of a normal, single waterwashed, refined soybean oil about as much as bleaching would have. The presence of sodium soap in refined oil, even up to 0.240%, did not effect the color of the bleached oil produced there‐from insofar as the Lovibond reading in the Wesson tintometer was concerned. However, the appearance of the oil bleached in the presence of excessive soap was different when the samples were viewed in reflected as well as transmitted light.