ANALYTICAL NOTES. VII.-Analytical Notes. BY A. B. NORTHCOTE AND A. II. CHURCH. 1. On the Action of Caustic Potash on the Phosphates. Experiments were undertaken on this subject with the view of discovering a bctter method than that generally adopted for esti- mating phosphoric acid,-the results obtained when the iron preci- pitate suspected to contain phosphoric acid is dissolved in hydrochloric acid the solution treated with tartaric acid and ammonia and subse- quently a salt of magnesia added to precipitate the phosphoric acid being frequently found to give erroneous conclusions because the tartaric acid solution often produces a precipitate in magnesia-salts probably of arnmonio-tartrate of magnesia without a trace of phos-phoric acid being present.It has hitherto been supposed that the phosphate of sesquioside of iron is but imperfectly attacked by solutions of the caustic alkalies but the extent of the decomposition which can be thus effected had not been submitted to a careful experimental inquiry. From the authors’ experiments it appears that by boiling the precipitate of iron with a sufficient excess of potash the phosphoric acid is completely transferred to the latter base; this method of proceeding is therefore recommended in the quantitative determi-nation of phosphoric acid It is proposed that the alkaline solution be deprived of alumina which might be introduced with the potash by the addition of silicate of potash and subsequently of excess of hydrochloric acid and ammonia. The filtered solution will then con- taiii the whole of the phosphoric acid which may be readily precipi..tated by a salt of magnesia. PROCEEDINGS OF THE CHElMlCAL SOCIETY. 2. On the behaviour of some Oxides with Caustic Potash in the presence of Oxide of Chromium. The influence of the association of sesquioxide of chromium with metallic oxides which by themselves are insoluble in solution of caustic potash is well known; the insoluble oxides being in some cases rendered soluble when thus associated while in the other cases they communicate their insolubility to the otherwise soluble oxide of chromium. The object of the inquiry instituted with reference to these results was to ascertain the exact conditions under which complete solution 01’ precipitation of the associated oxides occurs.It was found that com- plete solution takes place when the chromium as sesquioxide is associated with 40 per cent of iron as seaquioxide with 12.5 per cent of manganese 20 per cent of cobalt or 25 per cent of nickel as protoxides ;and that complete precipitation takes place when the chromium as sesquioxide is associated with 80 per cent of iron 60 per cent of manganese 50 per cent of cobalt or 50 per cent of nickel as protoxide. When cobalt and nickel however are. thus rendered soluble the result is not permanent; and ultimately not only does the oxide of cobalt or nickel become insoluble but it carries down with it some of the oxide of chromium. The other metallic oxides soluble in caustic potash were not found to be influenced in their relations with caustic potash by the pre- sence of sesquioxide of iron or to exert any influence upon that oxide.