THE NEW YORK JOURNAL OF PHARMACY 



not form. Since (Mn++) is divalent 

 and does form a soluble complex ion 

 with NH3, there ought not be any ques- 

 tion concerning its place in the new 

 grouping for it logically belongs to the 

 4th group together with Zn, Ni and Co. 



It is, therefore, not difficult to see 

 why Mn has uniformly been included in 

 the 4th group of basic components. On 

 the strength of a theoretical considera- 

 tion the classification is not incorrect. 

 In practice, however, the grouping has 

 not been justified. 



It is true that in the presence of a 

 large quantity of an ammonium salt in 

 a solution containing (Mn++), a pre- 

 cipitate of manganous hydroxide, Mn- 

 (OH)2, is not produced by ammonium 

 hydroxide immediately, or not at all if 

 all air (O) be excluded from the liquid. 

 However, in contact with the air (O), 

 a brown precipitate of manganic hydrox- 

 ide, MnO(OH)2, is soon observed to 

 form in the upper layers. 



Mn(OH), + O = MnO(OH), 



Mixing and warming assist the reac- 

 tion. The brown precipitate is not solu- 

 ble in ammonium salts or in NH4OH. 

 While in simple solutions of manganese 

 the quantity of this hydroxide formed 

 is not large, it is very markedly in- 

 creased when other hydroxides — those 

 of the 3rd group — are precipitated from 

 the same solution by NH^OH. Indeed, 

 with a large proportion of these com- 

 pounds present, all or nearly all of the 

 Mn in solution is precipitated together 

 with them. The gelatinous hydroxides 

 of Fe(ic), Al, Cr, not only hold some 

 of the Mn salt by absorption, but ap- 

 pear to have the power to carry down 

 the Mn hydroxide mechanically. 



From this it will be evident that in 

 the separation of the 3rd group from 

 the 4th, carried out in analysis, (Mm++) 

 cannot be completely retained in the 

 filtrate as a complex ion with NH,. Its 

 oxidation by air to (Mn4:-\-) cannot be 

 easily prevented while the contact action 

 of other hydroxides (group 3) is un- 

 avoidable. 



Since Mn cannot be kept out of the 

 3rd group, the question is can it be kept 

 out of the 4th? It has been found that 

 any Mn not precipitated by NH4OH in 

 the 3rd group can be easily oxidized by 

 a little H2O2 added to the alkaline fil- 

 trate, and removed by filtration after 

 heating. 



Mn(OH)o + H2O0 

 = MnO(OH)2 + H,0. 



The members of the 4th group arc 

 not precipitated from a strongly alka- 

 line solution by hydrogen peroxide. The 

 inevitable conclusion of this is that 

 manganese should be classed with the 

 3rd group as the manganic component 

 (M«4+). 



Identification* 



The reactions utilized for the identi- 

 fication of Mn depend, in the main, on 

 the property of its compounds to form 

 acidic ions when oxidized. The orig- 

 inal solid substance or the brown 

 MnO(OH)2 obtained in separations are 

 the best suited for treatment. 



I. — Oxidation to (MnO^=) by Fusion. 

 — The dry material is intimately mixed. 

 by trituration, with 3 parts of anhydrous 

 Na2C03, and the powder heated on a 

 platinum foil or in a capsule to fusion. 

 A crystal or two of KNO3 is then 

 dropped on the edge of the fused mass 

 and heating continued to cause a slight 

 foamino-. On cooling a green blue color 



