Double Salts

 Hello fam! Welcome to today’s lesson. We would focus our study today on trying to understand what a double salt is. While growing up in Nigeria, we had this substance that was used to wash snail before it is cooked. The substance was called “alum”. The substance was used to remove the snail slime so that the snail could easily be prepared in the pot.


This same alum was used sometimes for water purification. I remember a number of times that my mother would fetch water from untrustworthy sources due to scarcity of portable water in some parts of Nigeria and she would add this substance to coagulate the particles in the water and cause them to flocculate and subsequently be filtered out. 


My mother was a practicing chemist without even knowing it! It was years latter when I gained admission into the University of Nigeria Nsukka and started studying about water purification as a student whose major was Chemistry that I understood what my mother was doing back then when I was a child.


That substance that my mother was using in those days has the chemical formula; KAl(SO₄)₂·12H₂O. It is usually a white, hard solid. Do you notice that it contains both potassium and aluminum cations? This brings us to the definition of double salts.


A double salt is created by combining two distinct salts that crystallized in the same regular ionic lattice and include more than one cation or more than one anion. Other examples of double salts include; KCl.MgCl2.6H2O, KMnO4, CaBa(CO3)2 etc


When dissolved in water, a double salt is dissociated completely into all its ions. An aqueous solution of a double salt is composed of cations and anions which were in the initial double salt compound. Therefore, this dissociation produces simple ions in the aqueous solution.


Again, the double salt KNa(C4H4O6).4H2O, often known as Rochelle salt, is potassium sodium tartrate, tetrahydrate. Although it is occasionally employed as a buffer in the costmetics industry, it is most frequently used in the production of cheeses, jellies, and fruit butters.


We can see that the uses of Double salts are all around us. Tomorrow, we shall look at complex salts which are commonly referred to as complexes. As a prep, the image attached shows the difference between a complex salt and a double salt. See you tomorrow!


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