1884.] the Atomic Weight of Cerium. 153 



as basic sulphate, I evaporated the solution of the mixed nitrates of 

 cerium, lanthanum, and didymium, obtained in the first instance, to 

 complete dryness ; then heated the brown mass over a naked flame 

 until the brown colour entirely disappeared, and the residue became 

 a pale yellow. On treating this yellow residue with boiling dilute 

 nitric acid, the whole of the lanthanum and didymium was dissolved, 

 and nearly all the cerium was left as basic nitrate. 



When preparing the chloride I weighed out for each experiment 

 about 10'5 grms. of the air-dry oxalate, and put it in a rather wide 

 glass tube about 18 inches long. The tube was then placed in a 

 paraffin-bath and dry hydrochloric acid passed through it. The 

 hydrochloric acid gas was prepared in the following way : 20 parts 

 of oil of vitriol were mixed with 8 parts of water, and the mixture 

 was allowed to cool, it was then poured on to 12 parts of common 

 salt. The gas is not produced when the acid is thus diluted until a 

 gentle heat is applied, but when it is it comes so easily that it may 

 be regulated to come at any desired rate. The gas was first passed 

 through a Woulff's bottle containing oil of vitriol, and with three 

 tubulures, the third one being connected with an apparatus for 

 producing carbon dioxide, so that when necessary that gas could be 

 admitted without disconnecting any part of the apparatus, next 

 through two large (J -tubes containing calcium chloride, then again 

 through a bottle containing oil of vitriol, and lastly through a JJ~ 

 tube tilled with asbestos to catch any spray of sulphuric acid which 

 might be produced. The gas now entered the tube containing the 

 oxalate, and the excess, after passing through a sulphuric acid wash- 

 bottle, was absorbed in water. Soon after the hydrochloric acid 

 began to pass over the oxalate, water made its appearance at the 

 exit end of the tube. When the air was expelled heat was applied to 

 the bath, much water continued to come off, and was driven away by 

 heating the end of the tube. When the temperature of the bath rose 

 a little above 120 generally at 123 the oxalic acid began to 

 sublime to the end of the tube and condensed there in crystals, this 

 in its turn was driven away by heating the tube. As long as oxalic 

 acid was seen to come off the bath was kept between 120 and 130, 

 and all that did show itself as oxalic acid did so between these 

 limits. 



Afterwards the temperature of the bath was allowed to rfse 

 gradually to 200 ; there was no advantage in going higher, as the 

 paraffin evaporated away and a gas furnace can easily be regulated to 

 this temperature. I now transferred the substance, not yet com- 

 pletely converted into chloride, to another tube and continued the 

 process in an ordinary gas combustion furnace. The object now was 

 to so regulate the temperature that water was kept coming off 

 without increasing the heat so rapidly as to char the oxalate left 



