ORGANIC COMPOUNDS ETC. IX.-Action of Heat on Ferric Hydrate in presence of Water. By EDWARD DAVIES,F.C.S. Liverpool. HAVINCI noticed the occurrence of shilling particles apparently crystalline in precipitated ferric oxide which had been boiled for a considerable time I made the following experiments with a view to ascertain if the oxide could be obtained in the anhydrous state by boiling with water. Being aware that M. P6an de St. Gilles has investigated the properties of the oxide thus altered I con-fined myself to the determination of the amount of water. In the memoir above cited the oxide is spoken of as being a hydrate; it appears however that it is for the most part anhydrous. In the following experiments the ferric hydrate was prepared from ferric VOL.XIX. 0 DAVIES ON THE ACTION OF HEAT chloride. This was made by twice crystallising the ferrous chloride passing clilorine through a dilute solution and removing excess of chlorine by heating gently for some time. The water mas determined by careful ignition the absence of chlorine being proved by mixing a portion of the oxide with pure carbonate of sodium moisteuing with distilled water drying and gently igniting. The mass was boiled with water and on testing tbe solution only a very faint trace of chlorine was in any case detected. 1. Some solution of ferric chloride was Precipitated by am-monia the precipitate thoroughly washed with boiling water and then boiled with distilled water for 112 hours loss by evapo- ration being prevented by a coxidensing apparatus.The oxide became dense and lost its gelatinous appearance. It was again washed and dried at 100" C. On ignition-17.85 grains lost 1.03 grain or 5.7'7 % *Fe,0,H20 contains 10*11%. 2. The solution was precipitated as before and then boiled 100 hours without filtering from the chloride of ammonium thoroughly washed and dried at 100" C. 13.805 grain lost 056grain or 4.05 %. 3. On using hydrate of potassium in slight excess and treating as in No. 2,not filtering and boiling for 100 hours the dehydra- tion was not so complete contrary to expectation as the oxide in the former cases contained traces not to be estimated of ammonia. 25-77 grains lost 1.69 grains or 6.55 %. 4. Fearing that the loss might take place during the drying a portion of washed oxide was dried at 100"C.for at least an equal time being finely pulverised when dry and finally heated until it no longer lost weight after several hours' interval.15-64grains lost 1-43grains or 9-14.% being slightly below one equivalent. 5. Boilirig the oxide for long periods being inconvenient on * Fe = 56. ON FERRIC HPDBATE IN PRESENCE OF WATER. account of the bumping which occurs when the oxide has under- gone the physical change I resolved to try the effect of gently heating for a very prolonged period. The oxide was precipitated in thecold by ammonia washed with cold water and heated for 1004 hours at a temperature varying from 50-60' C. with frequent agitation. In a few days it became dense and brick-red in colour.It was washed with water at 50" C. and dried at the same temperature. 20-50 grains lost %4 grain or 4.09 %. 6. As the oxide in No. 5 contained a trace of ammonia hydrate of sodium was substituted as a precipitant the oxide was washed as before heated at 50-60" C. for 2,000 hours. The flask was closed and heated in an oil-bath. 38.46 grains lost 1-75 grains or 4-55 %. 19-20 *90grain or 4-68 %. It thus appears to be impossible to drive off all the water 4 to 5 per cent. adhering with extraordinary tenacity. The oxide thus prepared is brick-red very dense having a specific gravity of 4.545 that of red hematite being 4.7. It dissolves very slowly in nitric acid more readily in hydrochloric acid. Under the microscope the dried oxide presents angular masses translucent when very thin.Hoping to remove the unchanged hydrate with nitric acid 24.18 grains of oxide prepared as in No. 6 were heated to 5G0 @. for one hour with 2 oz of dilute nitric acid (1 part acid to 3 parts water). 4.77 grains dissolved and the residue was washed until no longer acid and dried at 50" C. 18.48 grains lost -65 or 3.517 %. These experiments show that the immense beds of haematite found in our own and other countries do not demand the suppc- sition of great heat to account for their anhydrous state. Probably much lower temperatures than that employed in the foregoing experiments acting in presence of water for a long period would bring about the same change. The various statements respecting the amount of water in ferric hydrate are thus explained that amount depending on the length of time during which the hydrate was exposed to the action of water and a more or leas elevated temperature.(32 BROWN ON VAPOUR-DENSITY DETERMINATIONS. Chromic and aluminic hydrates were also operated upon by precipitating them with ammonia washing and boiIing for 100 hours. No action appeared to take place ahminic hydrate retaining 3 eqs. of water and chromic hydrate 5 eqs. The hydrates retained their gelatinous condition.