Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV COMPOUNDS OF HYDROGEN AND OXYGEN; WATER AND HYDROGEN DIOXIDE Water Historical. Water was long regarded as an element. In 1781 Cavendish showed that it is formed by the union of hydrogen and oxygen. Being a believer in the phlogiston theory, however, he failed to interpret his results correctly. A few years later Lavoisier repeated Cavendish's experiments and showed that water must be regarded as a compound of hydrogen and oxygen. General methods employed for the determination of the composition of a compound. The composition of a compound may be determined by either of two general processes; these are known as analysis and synthesis. 1. Analysis is the process of decomposing a compound into its constituents and determining what these constituents are. The analysis is qualitative when it results in merely determining what elements compose the compound; it is quantitative when the exact percentage of each constituent is determined. Qualitative analysis must therefore precede quantitative analysis, for it must be known what elements are in a compound before a method can be devised for determining exactly how much of each is present. 2. Synthesis is the process of forming a compound from its constituent parts. It is therefore the reverse of analysis. Like analysis, it may be either qualitative or quantitative. Application of these methods to the determination of the composition of water. The determination of the composition of water is a matter of great interest not only because of the importance of the compound but also because the methods employed illustrate the general methods of analysis and synthesis. Methods based on analysis. The methods based on analysis may be either qualitative or quantitative in character. 1. Qualitative analysis. As was s...