Vegetable Pigments Research Articles

Fruit and Vegetable Pigments as Indicators

(1) Solutions of many fruit pigments act as indicators. (2) These solutions are easily prepared and stable, and the pH range of their color changes is in most cases conveniently near the neutral point (3) As liquid indicators they can be used in titrating acids, but not bases (4)Their greatest usefulness depends upon the fact that very satisfactory test papers can be made with them in a simple and inexpensive way.

Radiography of an Oil Painting

Having been asked to make a radiographic examination of an oil painting recently, I thought it might be of interest to publish photographs of the picture before and after restoration and one of the original radiograms. The picture was the property of a medical colleague and had been in his family for about thirty years. The original appearance is shown in Fig. 1. The picture was labelled “Portrait of an Artist by Frans Hals,” but was not believed by the owner to be such. Different persons with art knowledge seeing it said it was certainly not a Frans Hals, but stated that certain parts of the picture seemed much better drawn than others and showed finer workmanship and suggested that there might be an older painting underneath which had been worked up and added to, at a later date. Accordingly a radiogram of the head and shoulders on a 15 in. by 12 in. film was made, and revealed the condition shown in Fig. 2. The modern vegetable pigments of the visible painting being transparent, and the older mineral pigments showing up, a lace collar was seen taking the place of the ruff. The face seemed different in outline and the moustache did not appear.

The presence of vitamine A in the peel of common citrous fruits

About a year ago, preparations of orange peel were added to a diet otherwise free from the fat soluble vitamine. The possibility that such preparations might contain fat soluble A was based on the hypothesis of Steenbock that the fat soluble vitamine is a yellow vegetable pigment or a closely related chemical compound. The peels used for a determination of their fat soluble vitamine content were faultless and of the deepest yellow color. The outer surface of the dried peels was grated enough to break the tiny pockets which contain the yellow oil. Peels and gratings were then extracted on the water bath with ether and alcohol. These extracts were evaporated down to dryness. The gummy mass thus obtained was stirred thoroughly into a diet otherwise free from fat soluble vitamine and then fed to a number of white rats. The results yielded indubitable evidence that the waxes and oil of the orange peel are rich in the fat soluble vitamine. On this diet young rats have matured, mated, and raised young. Control experiments showed the diet, without the preparation of orange peel, to be free from fat soluble A. Experiments now in progress indicate that similar preparations made from lemon and grape fruit peel likewise contain the fat soluble vitamine.