394 Flora — Estimation of Cadmium taken as the Chloride. 



solvent. The deposits obtained from solutions to which were 

 added free phosphoric acid showed a slight tendency toward 

 sponginess. When hydrochloric acid was added, the deposits 

 were good but deposition was slow. The total volume in each 

 case was 45 cmS ; the amount of sodium pyrophosphate used was 

 9*5 grin. ; while the current potential was 7*8 volts. 

 The following results were obtained : 



Cd. Oiir't = N. D 10 „. Time. Cd. fd. Error. 



No. grm. Solvent. 



1. 0-1324 NH 4 OH, cone, l cm3 . 



2. 0-1324 H 2 S0 4 ,(L-4), 12 dps. 



3. 0-1342 H 3 P0 4 (sp.gr. 1'7), 15 dps. 



4. 0-1324 HC1, 1 :4, 15 dps. 



V. In Solutions containing Phosphates. 



With cadmium chloride, hydrogen disodic phosphate must 

 be used with even more care than with cadmium sulphate, if 

 deposits which are even slightly satisfactory are to be obtained ; 

 and even when used with caution, the tendency to form spongy 

 deposits is so persistent that this method is not to be recom- 

 mended where other methods are available. The following are 

 the solutions tried, the concentration being 45 cm3 throughout : 



amp. amp. 



mm. 



grm. 



grm. 



0-5 1-5 



15 



0-1327 



+ 0-0003 



0-75 2-25 



35 



0-1328 



+ 0-0004 



0-75-1-0 2-25-3-0 



30 



0-1331 



+ 0-0007 



0-7-0-5 2-1-1-5 



45 



0-1319 



— 0-0005 





Cd. 



HNa 2 P0 4 . 



H 3 P0 4 . Cur't = 



N. D 100 . E.M.F. 



Time. 



Cd. fd. 



Error 



N( 



). grm. 



grm. 



(sp. gr.-l # 7) amp. 



amp. vts. 



min. 



grm. 



grm. 



1. 



0-1059 



0-25 



5 cm s 2-0-3-0 



6-0-9-0 7-8 



15 



0-1082 



+ 0-0023 



2. 



0-1324 



0-25 



2 . 5 cm3 2-0-3-0 



6-0-9-0 7-8 



13 



0-1344 



+ 0-0020 



3. 



0-1324 



0-20 



10 dps 1-0 



3-0 7-8 



15 



0-1330 



+ 0-0006 



4. 



0-1324 



0-20 



6 dps 0-25 



0-75 7-8 



35 



0-1310 



— 0-0014 



Numbers 1 and 2 gave spongy deposits ; number 4 showed no 

 color upon testing the solution at the end of the operation 

 with hydrogen sulphide, but this test does not seem to be very 

 sensitive in this solution. Number 3 seems to represent the 

 best conditions. 



VI. In Solutions containing Oxalates. 



Several qualitative tests, using conditions identical with 

 those giving the least unsatisfactory deposits with cadmium 

 sulphate, were tried upon the cadmium chloride, with like 

 unsatisfactory results, so that the work upon the oxalate method 

 was not pursued further. 



VII. In Solutions containing Urea, etc. 



A few qualitative tests seemed to indicate that solutions con- 

 taining urea, formaldehyde or acetaldehyde would furnish very 

 satisfactory media for the estimation of cadmium, taken in 

 the form of the chloride, but further experimentation proved 

 these appearances to be deceptive. Under these conditions, 



