The filtrate was evaporated to expel the nitric acid and the residue taken up with water and tested for cadmium with hydrogen sulphide. An appreciable quantity was always found. This method of examination does not show the occluded silver nitrate. Another error which tends to lower the atomic weight found is due to the platinum crucibles used for filtering. If a silver nitrate solution is filtered through such a crucible there will be an increase in weight due to silver being deposited. This takes place in acidified solutions as well as in neutral ones. Washing with ammonia does not remove the deposit, but strong nitric acid does, the washings giving a test for silver. Whether the depositing of silver is due to the action of spongy platinum in contact with the compact metal of the crucible or to some impurity in the platinum sponge was not determined, but the former seems by far the most probable. The increase in weight during the time required for filtering a determination must have been quite small however. The samples of cadmium chloride employed for determinations XX and XXI were prepared by burning cadmium in a current of chlorine. The glass tube used was attached somewhat and the solution of the chloride was very slightly turbid in each case. The turbidity was so slight however, that no very serious error could have resulted from it, particularly as it was probably partly counterbalanced by the formation of some potassium chloride. For more accurate work, it should have been made and redistilled in a porcelain tube. These two samples were tested for free chlorine with potassium iodide and starch paste, but none was found. Some of the specimens of chloride prepared by fusion in a current of hydrochloric acid were found to be neutral, using tropaeolin as an indicator. As nearly as can be judged, the above errors would probably counterbalance each other to a great extent, and thus give a fairly close approximation to the atomic weight of cadmium when the average of all the determinations is taken. The value 112.383 thus obtained can only be regarded as tentative. The Bromide method. Huntington (Proc. Amer. Acad. 11.28) working under the direction of J. P. Cooke, determined the ratio of cadmium bromide to silver bromide and using the total quantities for the calculation the result for the atomic weight of cadmium is 112.239. He also determined the ratio of cadmium bromide to silver, obtaining 112.245 for the atomic weight of cadmium. The work which will now be described was carried out very much like the work described under the chloride method. The ratio of cadmium bromide to silver bromide was investigated. Preparation of Cadmium Bromide and Hydrobromic Acid.