Cumulative Subject preparation from

The key to earning a successful grade on a chemistry test is to be actively involved in learning the content and to be well-prepared for every class. Chemistry is a cumulative subject, meaning that each section builds on the one before it. Preparation cannot begin the night before the test, but must be ongoing from the first day of class to the last day of class. 

Whilst the test described above is a common way in which an attempt is made at predictive identification of those substances or products with significant skin-irritation potential, other information can also be used. Consideration is given to structure-activity relationships, although it must be said that this subject is in its infancy for skin irritants (Whittle et al. 1996 Barratt 1996). Data may also come from non-standard animal tests, predictive human tests and from human experience. These may cover either acute and/or cumulative irritant responses in skin. It is also possible for manufacturers to use data from in vitro studies. Lastly, where the product is a mixture of two or more substances [a preparation in European Union (EU) terminology], the manufacturer may elect to calculate the likely irritancy on the basis of the knowledge of the skin irritancy of the component substances and the concentration at which they occur in the product. For certain types of product, this process has been formalised in the EU as the conventional method (European Community 1988). 

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