in other words, on the basis that one molecule of potassium permanganate will oxidize one and two-thirds molecules of nitric oxide: (KMnO_{4} = 1-2/3 NO). The method of using the apparatus is simple. The nitrate is placed in B, and the joints made tight, except that at _f_, which is left open. A current of carbon dioxide is passed through the apparatus until all of the air has been displaced. Connection is then made at _f_, and soon afterward the current of carbon dioxide is shut off at _d_. The flask, B, is now heated as long as may be necessary in order to produce, on cooling, the diminished pressure required for the introduction of the ferrous chloride and hydrochloric acid. Before removing the flame, the joint at _f_ is closed to prevent the return of the permanganate solution. As soon as the flask, B, has become sufficiently cool, the ferrous chloride and hydrochloric acid are introduced through the tube, _a_ (which has been full of water from the first), in the same manner and quantities as in the well-known Tiemann-Schulze method. The pinch cock at _d_ is then opened, and the apparatus allowed to fill with carbon dioxide. When the pressure has become sufficient to force the gas through the solution of permanganate, the pinch cock at _f_ is removed. It should be opened only slightly and with great caution at first, unless one is certain that the pressure is sufficient. If the pressure is insufficient, the fact will be made apparent by a rise of the permanganate in the small internal tube. The flow of carbon dioxide is now reduced to a very slow current, or entirely cut off. The contents of B are slowly heated, until the decomposition of the nitrate is complete and the greater part of the nitric oxide has been expelled, when the apparatus is again closed at _f_ and _d_, and allowed to cool. The tube, _a_, is then washed out, by the introduction through it into B of a few cubic centimeters of strong hydrochloric acid. The process of filling the apparatus with carbon dioxide, and of heating the contents of B, is repeated. When it becomes apparent, from the light color of the liquid in B, that all of the nitric oxide has been expelled from it, the current of carbon dioxide is increased and the heating discontinued. Care must be taken, however, not to admit too strong a current of carbon dioxide, lest some of the nitric oxide should be forced unabsorbed through the permanganate solution. It is also necessary, for the same reason, to avoid too rapid heating during the decomposition of the nitrate. When all of the nitric oxide has been forced into the solution of permanganate, the determination is made in the manner already described.