282 Dr. Playfair on the NitroprusstdeSj 



V. 14.-68 grs. gave 2-80 Fe^ O^ and 9-44. grs. Ag CI. 

 r VI. 13-16 grs. gave 2-43 Fe^QS and 8'535 Ag CI. 

 \ VII. 24-41 grs. gave 4-54 Fe^O^ and 15-79 Ag CI. 



VIII. 15-21 grs. gave 2-88 Fe^ O^ and 9*89 Ag CI. 

 IX. 13-60 grs. gave 2-60 Fe^O^ and 8*80 Ag CI. 



X. 8-81 grs. gave 1-69 Fe^ O^ and 5-59 Ag CI. 



The combustions were made partly with chromate of lead, 

 partly with oxide of copper. 



I. 12-05 grs. gave 6-08 grs. CO^ and 0-10 gr. HO. 

 II. 12-195 grs. gave 6-10 CO'^ and 0-08 HO. 

 IV. 8-10 grs. gave 4-03 CO^ and 0-09 HO. 

 V. 10-35 grs. gave 5-13 CO^ and 0*21 HO. 

 VI. 14-52 grs. gave 7*18 CO^ and 0-05 HO. 

 VIII. 9-56 grs. gave 4-85 CO^ and 0-04 HO. 



IX. 10-835 grs. gave 5*50 CO^ and 0-10 HO. 



100-00 100-00 100-00 100-00 



If we assume the mean iron, 13-36, to represent the true 

 quantity, then the silver to correspond to it in atomic propor- 

 tion should have been 51-53, whereas there is only 48*78. 

 Hence there is 0-72 of iron in excess over the equivalent 

 quantity; this excess corresponds to y'^jth of an equivalent. 

 Again, supposing the carbon to be in the same proportion to 

 the silver as in thenitroprussides, there should have been 13*0, 

 so that there is an excess of 0-64. The excess of iron and of 

 carbon is therefore almost exactly as 1 equiv. : 4 equivs., or 

 viewing the carbon as representing cyanogen as 1 : 2. On 

 this view the amount of impurity in the silver salt is 2-10 per 



