g$ ALUMINOUS CHALYBEATE SPRING IN I. OF WIGHT. 



Proportion of 3. It was therefore necessary to separate the iron previous 

 sulphate of f ^ e precipitation of the lime. This was done in one 

 instance by prussiate of potash, and in another by succinate 

 of ammonia. I shall not trouble the society with a detail 

 of these operations. It will be sufficient to state, that the 

 two. most unexceptionable experiments indicated the one 

 $ grains, and the other 8'3 grains of oxalate of lime, dried 

 Ht l6o°, for each pint of the water, making an average of 

 8*15 grains of oxalate of lime, or 10*17 grains of sulphate 

 of lime dried at l6o°; or 7'94 grains of the same salt dried 

 at a red heat*. 



Sect. 



.obtain the oxalate of lime pure, it was necessary to calcine the pre- 

 cipitate so as to drive off the oxalic acid, to redissolve the residue iii 

 muriatic acid, and to precipitate the lime again by oxalate of ammo- 

 nia. The small quantity of iron present did not then interfere, and 

 this process, however circuitous, proVed tolerably accurate. 



I was drawn by this part of the subject into an experimental inquiry 

 respecting the action of oxalate of ammonia on solutions of iron, and 

 the unfitness of this test for the precipitation of lime when iron is 

 present, the principal results of which I shall state summarily. 



1. If lo a strong solution of sulphate of iron a small quantity of 

 sulphate of lime be added, and then a little oxalate of ammonia, no 

 precipitate or cloudiness appears; while the same quantities of sul- 

 phate of lime anil oxalate of ammonia, added to a bulk of water equal 

 to that of the solution of iron, instantly form a precipitate. 



2. If oxalate of ammonia be added to a solution of sulphate of iron, 

 a bright yellow colour is produced; and presently after this a copious 

 white pit cipitate appears, which, in subsiding, assumes a pale lemon 

 colour. If, at the moment the cloud is forming, the vessel be scratch- 

 ed with any pointed instrument, white lines appear, as in the pre- 

 cipitation of magnesia from carbonic acid by phosphoric acid. 



a. This precipitate being washed, and gently heated over a lamp, 

 assumes a bright cinnamon colour, and becomes magnetic, jn conse- 

 quence, no doubt, cf the carbonization of the oxalic acid; and these 

 changes take place at a heat much inferior to ignition. 



4. lfasolution of potash be added to the washed precipitate, previous 

 to the application of heat, a strot'g smell of ammonia arises, and the 

 oxide passes to a dark grayish colour, showing that the precipitate is 

 u triple salt of oxalic acid, iron, and ammonia. 



* J avail myself, in farming these various estimates, of the propoj--! 

 tions given by Dr. Henry, in his valuable 'Analysis of several varieties 

 of Sea Salt' (published in the Philusop lical Transactions for 1SJ0, 

 pnge 114), where he states that 10Q grains of iguited sulphate of lime 



(which 



