Where is Al2O3 in Al2(SO4)3 coming from? [closed]








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let me know where is Al2O3 in Al2(SO4)3 containing from? as we know there is 17-18% Al2O3 in commonly Al2(SO4)3 product. 
is it because low convertion of reaction Al2O3 + 3H2SO4 = Al2(SO4)3 + 3H2O, or something? 


if i using Al(OH)3 to convert Al2(SO4)3, 2Al(OH)3 + 3H2SO4 = Al2(SO4)3 + 6H2O, is it still happen 17-18% containing Al2O3 in Al2(SO3)3 because dehydration reaction of 2Al(OH)3 = Al2O3 + 3H2O?




You are referring to very old analytical methods and analysis. In older times, many analyses were *reported* as oxides. This practice comes from gravimetric analysis. This practice continues today in fertilizers analysis and in some other industries. Coming to your question, there is **no** Al$\_2$O$\_3$ unit per se however the purity of aluminum sulfate may be quoted as aluminum oxide. Just do a simple mole calculation using the relation to determine the actual purity of aluminium sulfate. Just keep in mind, quoting percentage of oxides is purely historical, but you can easily do calculations as follows.


1 mol Al$\_2$O$\_3$ $\equiv$ 1 mol Al$\_2$SO$\_4$ $\equiv$ 1 mol Al$\_2$SO$\_4$. $x$H$\_2$O


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