34 Dr. Schunck on the Formation of Indigo-blue. 



from this precipitate gave with a little ammonia a second preci- 

 pitate of a rather paler yellow colour, which was collected on a 

 filter, washed with alcohol, and dried in the same manner as the 

 first. The analyses III. and IV. were made with this precipitate. 

 The following results were obtained : — 



I. 1-0120 grm. burnt with oxide of copper and chlorate of 

 potash, gave 0-7590 grm. carbonic acid and 0-1885 water. 



1-0330 grm. burnt with soda-lime gaveT)-0580 grm. platinum. 

 0-6385 grm. gave 0-5140 grm. sulphate of lead. 



II. 0-8845 grm. gave 0-5040 grm. carbonic acid. 



1-1100 grm. burnt with soda-lime gave 0-1260 grm. chloride 

 of platinum and ammonium. 



0-3490 grm. gave 0-3260 grm. sulphate of lead. 



III. 1-3315 grm, gave 0-9380 grm. carbonic acid and 0-2535 

 water. 



1-6295 grm. gave 0-2145 grm. chloride of platinum and 

 ammonium. 



0-8550 grm. gave 0-7005 grm. sulphate of lead. 



IV. 0-9520 grm. gave 0-6345 grm. carbonic acid and 0-1715 

 water. 



1-2490 grm. gave 0-0640 grm. platinum." 

 0-5335 grm. gave 0-4495 grm. sulphate of lead. 

 These numbers correspond in 100 parts to — 



100-00 100-00 100-00 



After deducting the oxide of lead, the relative proportions of 

 the other constituents are expressed by the following numbers : — 



100-00 10000 10000 



These numbers conduct, as will be seen, to two difi'erent for- 

 mula?. Tlie numbers of the first two determinations lead to the 

 formula C^^jiai NO"^', those of the last two to the formula 

 C^^II-'*^NO^, as a comparison of the numbers found by experi- 

 ment with those required by the respective formulae will show. 



