Flora — Estimation of Cadmium taken as the Sulphate. 273 



In Nos. 1 and 3 a small amount of dilute sulphuric acid was 

 added to increase the conductivity of the solution, but the time 

 was not reduced thereby, while the resulting deposit was 

 slightly spongy. 



In So. 5 the cadmium was not quite all precipitated. 



In No. 7 the precipitate was spongy. 



V. In Solutions containing Phosphates. 



The use of a solution containing the orthophosphates dis- 

 solved iu phosphoric acid has. been recommended by Smith*, 

 and this solution was next tried. The following results will 

 show the scope of the modifications tried : 



Cd. HoP0 4 Total Cd. 



taken. HNA 2 P0 4 . (1:7) vol. Cur't.= N.D 100 . E.M.F. Time. fd. Error. 



No. grni. grm. cm. cm. amp. amp. vts. min. grm. grm. 



1. 0-1491 0-5 1-0 75 1-0,-1 '-2 3'0- 3*6 8 20 0*1477 — 0*0014 



2. 04491 0-5 5-0 75 2*0-2*5 60- 7*5 8 23 0*1496 + 0*0005 



3. 0-1491 0-5 5-0 75 2-0-1-5 6*0- 4*5 8 30 0'1508 + 0*0017 



4. 0-1491 0-5 3-0 75 2*5 7*5 12 25 0-1502 + 0*0011 



5. 0-1491 0-5 4-0 75 2*5 7*5 8 25 0*1485 — 0'0006 

 C. 0-1491 95 2-0 75 2*5 7*5 12 35 0*1501 +0*0010 



7. 0-1864 0-25 2*0 75 2*0-3*0 6*0- 9*0 12 40 0*1861 —0*0003 



8. 0-1491 0*3 1-5 75 3"5 10-5 12 30 0*1502 +0*0011 



9. 0*1019 0*25 5-0 75 2-5-3*0 7*5-9*0 7*8 30 0*1024 +0*0005 



10. 0*1019 0*25 5*0 75 3*0-3*5 9*0-10-5 7'8 30 0*1027 +0*0008 



11. 0*1223 0*2 5*0 75 3*0-3*5 9*0-10*5 7*8 40 0*1221 —0*0002 



No. 1.— Not all out, No. 2.— Slight yellow color with H 2 S. 

 No. 3.— Slight yellow with H 2 S. No. 4.— Spongy. No. 5.— 

 Not all out. No. 6.— Spongy. No. 10.— Spongy. No. 11.— 

 Slight test with H 2 S. 



From this series of experiments it may be seen that the 

 method may be made to give fair results if the following con- 

 ditions are closely adhered to : for a total volume of 75 cm3 , the 

 cadmium is precipitated with 0*25 grm. of hydrogen disodic 

 phosphate, 5 cm3 of phosphoric acid (sp. gr. = 1*7) added, and 

 the solution electrolyzed with a current of about 8 volts poten- 

 tial. If the normal current density does not exceed 9 amperes, 

 the deposit will be fair, and complete in about 30 minutes. 



YI. In Solutions containing Oxalates. 



Much work was expended upon the oxalate method, but in 

 spite of this, a satisfactory deposit could not be obtained. 

 When ammonium oxalate was present, even in small amounts, 

 the deposit was very spongy : while the use of sodium oxalate 

 alone, when carried down even to the smallest excess possible 

 *Am. Ch. J., xii, 329 (1890). 



