1. From the method of preparation of platinum, what metal is likely to be alloyed with it? 2. The "platinum chloride" of the laboratory is made by dissolving platinum in aqua regia. What is the compound? 3. How would you expect potassium aurate and platinate to be formed? What precautions would this suggest in the use of platinum vessels? 4. Why must gold ores be roasted in the chlorination process? CHAPTER XXXII SOME SIMPLE ORGANIC COMPOUNDS ~Division of chemistry into organic and inorganic.~ Chemistry is usually divided into two great divisions,--organic and inorganic. The original significance of these terms was entirely different from the meaning which they have at the present time. 1. _Original significance._ The division into organic and inorganic was originally made because it was believed that those substances which constitute the essential parts of living organisms were built up under the influence of the life force of the organism. Such substances, therefore, should be regarded as different from those compounds prepared in the laboratory or formed from the inorganic or mineral constituents of the earth. In accordance with this view organic chemistry included those substances formed by living organisms. Inorganic chemistry, on the other hand, included all substances formed from the mineral portions of the earth. In 1828 the German chemist Woehler prepared urea, a typical organic compound, from inorganic materials. The synthesis of other so-called organic compounds followed, and at present it is known that the same chemical laws apply to all substances whether formed in the living organism or prepared in the laboratory from inorganic constituents. The terms "organic" and "inorganic" have therefore lost their original significance. 2. _Present significance._ The great majority of the compounds found in living organisms contain carbon, and the term "organic chemistry," as used at present, includes not only these compounds but all compounds of carbon. _Organic chemistry_ has become, therefore, _the chemistry of the compounds of carbon_, all other substances being treated under the head of inorganic chemistry. This separation of the compounds of carbon into a group by themselves is made almost necessary by their great number, over one hundred thousand having been recorded. For convenience some of the simpler carbon compounds, such as the oxides and the carbonates, are usually discussed in inorganic chemistry.