The microcosmic salt bead dissolves almost every oxide except silica, SiO_{2}, and this is seen to float about in the melted mass. This is used as a test for silica. ~Examination with Co(NO_{3})_{2}.~--If after examination on the Ch. _per se_, a white infusible residue remains, it is moistened with a drop of cobalt nitrate Co(NO_{3})_{2} and re-ignited before the Bp., when a change of color will be observed. This change in color is owing to the fact that the heat of the Bp. flame decomposes the cobalt nitrate, nitric acid being driven off, and the remaining CoO forming with the oxide of the residue a colored mass. _Illustrations._ Ignite before the Bp. on Ch. the following oxides,--allow to cool, add a drop of Co(NO_{3})_{2}, re-ignite, and note color,--aluminum, magnesium, zinc, and calcium. Care should be taken to thoroughly ignite before adding the cobalt nitrate solution. With the six methods of examination just given almost every simple substance can be detected, but should any doubt remain, a few simple tests in the "liquid way" will be sufficient to substantiate the blowpipe examination. CHAPTER III GENERAL REACTIONS FOR THE DETECTION OF THE METALLIC ELEMENTS IN SIMPLE COMPOUNDS For the sake of convenience, rather than for scientific reasons, the following compounds have been arranged in alphabetic order. Also the oxides of the elements have been taken, since they exhibit the reactions to best advantage. The student should work through carefully each one of the tests and satisfy himself as to the characteristic reactions of the various elements, for only in this way can he expect to recognize the substances when presented to him as "unknowns." It is advisable to provide a note-book and rule it as follows:--