references are to be found on the subject of electrodialysis, and new applications and uses are numerous.Most of the data reported in the present paper have resulted from research necessary to obtain a substance of a certain purity for use in some other investigation.The apparatus used in the electrodialysis experiments was essentially that described by Holmes and Elder (4). In all experiments a piece of platinum foil was placed between the carbon anode and the filter paper. Parchment and Cellophane membranes were used throughout the investigation. Electrodialysis of CaseinSamples of both acid and rennin casein were obtained from the research laboratory of the Borden Company. The ash content of acid casein before electrodialysis was 3.69 per cent and after 56 hours of electrodialysis was 0.067 per cent, a 98.4 per cent removal of ash. The acid casein (8.41 grams) was suspended in dilute acetic acid and diluted to 850 cc. Ammeter readings varied from 0.22 ampere at the start to 0.027 ampere at the end. The maximum and minimum temperatures within the cell were 45°and 25°C ., respectively. A sliding resistance was used to keep the cell from heating too much. During electrodialysis a horny material deposited on the cathode membrane, and, when dried, had an ash content of 0.069 per cent.