[Guillem_dlc]

Hello, a formulation question, I am reviewing summary documents of the 2005 IUPAC recommendations and I have the following doubts:

• It speaks of 3 types of nomenclature: systematic (composition, addition and substitution), semi-systematic and traditional so I see the most used is the systematic of both composition and addition and in some cases even the traditional one is allowed, but where the Semisystemic some example??
• In one of the summaries, I find that the iupac does not allow the hyposulfuric acid, when for oxoacids if it allows the traditional nomenclature, then because if it allows the sulfuric acid and the sulfuric acid (valences 4 and 6 of the sulfur), why is it not allowed? hyposulfuric for valence +2
• As I understood the meta and ortho prefixes (applicable to groups 15 and 16) refer to the acid having more or less water molecule content and in the case of a heteroatom of group 15 (odd Valencia), the prefix ortho is omitted, that is to say we have with P (+5) H3PO4 orthoboric acid but ortho is not used ie boric acid and HPO3 with less water content and it is boric acid. However, if it is an element of group 16 (even valence), it is omitted when naming the meta prefix, that is, the metasulfuric acid with the lowest water content is H2SO4 and sulfuric acid is said and the higher content of H4SO5 will be orthosulfuric acid. So I thought I had it clear, but in one of these summaries of iupac they call H4SiO4 silicic acid and H2SiO3 metasilic acid, that is, omitting the prefix ortho instead of the goal instead of omitting the goal, as it is done when naming the acids of sulfur. That is, in sulfur, the nomenclature without prefixes corresponds to the lower content water and silicon, it seems that the nomenclature without prefix corresponds to the acid with the highest water content. Can you explain me

Thanks