IRON AND ALKALINE EARTH GROUPS NICKERSON, 97 



5. Procedure. — Divide the above solution into two parts, 

 and to one add an excess of HCoHgOg and a few cc. of 

 Pb(C2H30^)^ solution. A yellow precipitate indicates Cr. 

 To the other portion add an excess of dilute H CI, and* then a 

 slight excess of NH^OH. Warm and set aside. A white 

 flocculent precipitate is Al(OH)o. 



6. Treatment of filtrate from 1. — Acidify a small por- 

 tion of the solution with dilute HNOg and test for P O/" ions 

 with (N HJgMoO^ If a yellow precipitate is formed, treat 

 the remainder of the solution with H„S. A white precipitate 

 is ZnS. If no PO4"' ions are found, see 7. 



Notes. — 1. The addition of even a slight excess of NH^OH in 

 1, is sufficient to convert the Zn into the soluble complex compound 

 Zn(NHg)^(0H)2, which passes through into the filtrate and is 

 removed by H^S. 



2. If the addition of (NH^)2MoO^ shows the presence of PO/" 

 ions, then the solution after the removal of Zn contains only tlie 

 metals of the alkali group. 



7. Procedure. — If PO4'" ions are not found in 6, add 

 solution to filtrate from 3, warm, and to the warm solution 

 add an excess of H, S. Filter: 



Notes. — 1. If P O4'" ions are not found in 6, the sohition will 

 contain only those ions in excess of what was necessary to combine 

 with the PO^'" ions precipitated in 1. They may consist of: Zn, 

 Mn, Ni, Co, Ba, Sr, Ca, Mg, K and Na. 



8. Procedure. — Treat precipitate with a small amount of 

 dilute H CI (1 part H CI 1.12 to 5 parts water) . Residue may 

 be Ni S and Co S. Separate in usual way. Treatment of 



