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SULPHUR.

by various processes we are able to obtain compoundsof nitrogen with most other elements, setting out withthis acid as a source of nitrogen ; for it seems thatnitrogen hardly ever will combine with an element,except when it is being evolved or set at liberty by thedecomposition of a substance in which it was alreadycombined with some other element.

105. There are three other elements deserving noticewhich, like nitrogen, are of little interest in themselves,but which, by combining with other substances, formimportant compounds ; these are sulphur, chlorine, andphosphorus.

106. The properties of Sulphur , or brimstone, arefamiliar to every one; it is a pale yellow solid substanceinsoluble in water, having neither taste nor smell whencold, melting easily when warmed, and catching firevery readily, burning with a pale blue flame, and givingout at the same time a peculiar and very disagreeablesmell. The compounds which sulphur forms withoxygen and also with hydrogen are the principal whichdemand attention.

107. Sulphur, like nitrogen, is able to combine withoxygen in several proportions, and hence forms severaldistinct compounds ; it is only necessary to describe twoof them, sulphurous acid, and sulphuric acid or oil ofvitriol.

108. When sulphur is burnt in the air, it forms sul-phurous acid gas, a transparent invisible gas, possessinga very strong and suffocating smell; it is easily dis-