Vicky Silviana的实验室

 Welcome back! Now, let's first dissolve some CoSO4 or MnSO4 into 5M sulfuric acid, together with ammonium alum. To do so, add 0.02 mol of ammonium sulfate and aluminium sulfate to 100mL of acid, then 0.02 mol of the transition metal one. Now heat to dissolve these all, then cool down for a night to let excess alum crystallize. They are just alum of course. From now on different strategies are needed for them. Mn: Mn3+ is stable when H+ is very concentrated and Mn2+ is much more concentrated than Mn3+, so we should electrolysis without partitioning, and only a little part of Mn2+ is oxidized. Finally solution looks like this: Finely red. Cool this solution down to 0 degree celcius or so gives orange crystals, and throwing alum into initial solution gives it a cover. All crystals MUST be dried carefully! Solution can be used again of course. It seems that crystals are unstable when [Mn3+] is too high. This is hard to control. Reduction is simple though, just carefully add oxalic aci...

 Vanadium is the 23rd element, lies in period 4 and group VB. Being an early transition metal it is somewhat similar to main group elements, especially P, but can also be reduced to the +3 and +2 states, common in transition metals. Its +4 state mainly exist as [VO]2+ which is a stable terminal oxo complex. It is somewhat expensive and toxic, so use carefully. Before exploring more, I wanna make V3+ and V2+ as double salts. I obtained this element as sodium metavanadate (NaVO3), which makes it a little troublesome to remove unwanted Na+. If you can get NH4VO3 and you want an ammonium salt product, just add acid and reduce it. NaVO3 is a fine white powder that dissolves slowly in water. Heat to dissolve it. Then add sulfuric acid carefully until pH becomes 2~3. Now the solution is dark yellow and much red stuff precipitated. The solid is V2O5, and is very sticky. Filtering is quite hard and sick, so just pour off the liquid carefully, add water, then pour again, to wash it. You may ...

A2B(SO4)2.6H2O where A is univalent, K or larger, normally NH4, and B is divalent. B must exist as hexaaquo ion. So, there is in fact no water of crystallization. These compounds are usually highly stable due to crosslinking hydrogen bonds, being resistant to oxidation and erosion in air even if B is Cr, Fe or V. Simply mix the sulfates in solution, and they quickly reacts to form double salt crystals. Even solid sulfates are OK, as a saturated solution of Tutton's salt is not saturated for the simple salts. Monoclinic. If you use no fishing string like me, you may get two different shapes due to different directions(see below), and you can manually turn the diamond one to the brick one by simply turning the seed upside down(?). It seems that +3 cation strongly impacts transparency. Note: ratios below are that of mass of saturated solution at ambient conditions, NOT solid as it would be very hard to prepare or recycle. This doesn't matter in most cases, but if you wanna use mor...

About the ions Although +3 oxidation state exists for all transition metals between Sc and Co, they are almost always unfriendly. While the common Cr3+ is stable and Fe3+ is mildly oxidizing and highly acidic, the closely related Mn3+ and Co3+ are exceedingly unstable at normal ranges. Instead of directly telling you the phenomena I'd like to show thermodynamic data first. E0(Mn3+/Mn2+)=+1.49V E0(MnO2/Mn3+)=+0.95V E0(Co3+/Co2+)=+1.92V E0(O2/H2O)=+1.229V The first two lines may need an explanation: if we make a battery of the first minus the second, it turns out that Mn3+ can release much electricity(energy) when it becomes Mn2+ and MnO2, as the net potential is highly positive, about +0.5V. That is to say, Mn3+ is very prone to disproportionation. The third line could just be called horrible: Co3+ is much higher than O2, so oxidizing water is quite easy! In fact this is just at pH=0 or [H+]=1mol/L, and things become much worse at neutral pH as H+ lies on the right side of the equat...