Some conventions regarding components

There are two ways in which the way chemical formulas are used which may 

Aqueous species are used in both hydrated and nonhydrated forms. For example, dissolved silica is written as Si02(a ) or as Si02-2H20 (or H4Si04, which is the same thing). 

Formulas can be presented in various multiples. For example forsterite may be listed as Mg2Si04 or as MgSio 502. 

These are quite simple relationships, but they can cause quite a bit of confusion. 

One way to write the dissolution reaction for quartz is SiOjCs) +2H2O = H4Si04(a ) Another way to write the same reaction is 

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Another comparatively recent development is poly(butylene terephthalate) heavily filled for electroplating applications. For a plastic it has unusually high density and so gives components much heavier than would be made with conventional unfilled polymers. In some instances this is regarded as desirable—the heavier mouldings are closer in weight and in feel to components cast or machined from metal. Since they are more familiar they are perceived to be of better quality—a concept apparently quite important for uses such as bathroom fittings and plumbers requisites. 

Enzymatic digestion has some advantages over conventional sample pretreatment procedures based on acid or alkaline digestion thus, the former uses mild conditions as regards temperature and pH, which avoids potential analyte losses by volatilization or ohemical transformation to other species, and reduces the risk of contamination. In addition, the selectivity of enzyme catalysis is a powerful tool for distinguishing between fractions of elements associated with different components of the matrix as enzymes act on oertain ohemical bonds only. 

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