1904.] The Chemical Dynamics of Photographic Development. 471 



Table XV. Ferrous Fluoride, N/10. 



Temp. 13 C. 



Time. 



45 '0 mins. 

 90-0 

 135-0 



280-0 



co 



7- 



0-50 

 1-00 

 1-35 

 1-72 

 2-00 



* 7,-7 



0-0028 

 0-0033 

 0-0036 

 0-00303 



K = 0-0032 



Time. 



15*0 mins. 

 60-0 

 90-0 

 120-0 



.GO 



Temp. 20 C. 



0-204 



0-895 



1-22 



1-36 



2-00 



0-0030 

 0-0043 

 0-0045 

 0-0041 



K = 0-0043 



Hence, comparing results, 



Temp. K Ferrous oxalate. Ferrous fluoride. Rat.io. 



13 C. 0-060 0-0032 187 



20 C. 0-071 0-0043 16-5 



This indicates that ferrous fluoride has a somewhat higher tempera- 

 ture-coefficient than ferrous oxalate. 



Ferrous Citrate. This is a good developer for chloride plates, -but 

 develops silver bromide very slowly. For the plates employed 

 y x =3-40, and K for ferrous oxalate at 20 C. - 0-0487. 



It was found that here also the density ratios and the inertia were 

 independent of the time of development. For the velocity at 20 C. 



Table XVI. Ferrous Citrate, N/10. 



Time. 



60-0 mins. 

 120-0 

 240-0 



oo 



7- 



0-474 

 0-720 

 1-40 

 3-40 



0-0011 

 0-0009 

 0-00096 



K - 0-0010 



Whence for table of relative efficiencies at 20 C. 



Developer. Efficiency = K 



Ferrous citrate 1*00 



Ferrous fluoride 2'95 



Ferrous oxalate 48*7 



