The principal operations with the Blowpipe may be explained briefly as follows: 

(a.) By Ignition is meant the exposure of a substance to such a degree of heat, that it glows or emits light, or becomes red-hot.  Its greatest value is in the separation of a volatile substance from one less volatile, or one which is entirely fixed at the temperature of the flame.  In this case we only take cognizance of the latter or fixed substance, although in many instances we make use of ignition for the purpose of changing the conditions of a substance, for example, the sesquioxide of chromium (Cr^{2}O^{3}) in its insoluble modification; and as a preliminary examination for the purpose of ascertaining whether the subject of inquiry be a combination of an organic or inorganic nature.

The apparatus used for this purpose are crucibles of platinum or silver, platinum foil, a platinum spoon, platinum wire or tongs, charcoal, glass tubes, and iron spoons.

(b.) Sublimation is that process by which we convert a solid substance into vapor by means of a strong heat.  These vapors are condensed by refrigeration into the solid form.  It may be termed a distillation of a solid substance.  Sublimation is of great consequence in the detection of many substances; for instance, arsenic, antimony, mercury, etc.

The apparatus used for the purposes of sublimation consist of glass tubes closed at one end.

(c.) Fusion.—­Many substances when exposed to a certain degree of heat lose their solid form, and are converted into a liquid.  Those substances which do not become converted into the liquid state by heat, are said to be infusible.  It is a convenient classification to arrange substances into those which are fusible with difficulty, and those which are easily fusible.  Very often we resort to fusion for the purpose of decomposing a substance, or to cause it to enter into other combinations, by which means it is the more readily detected.  If insoluble substances are fused with others more fusible (reagents) for the purpose of causing a combination which is soluble in water and acids, the operation is termed unclosing.  These substances are particularly the silicates and the sulphates of the alkaline earths.  The usual reagents resorted to for this purpose are carbonate of soda (NaO, Co^{2}), carbonate of potash (Ko, Co^{2}), or still better, a mixture of the two in equal parts.  In some cases we use the hydrate of barytes (BaO, Ho) and the bisulphate of potash (Ko, 2so^{3}).  The platinum spoon is generally used for this manipulation.

Substances are exposed to fusion for the purpose of getting a new combination which has such distinctive characteristics that we can class it under a certain group; or for the purpose of ascertaining at once what the substance may be.  The reagents used for this purpose are borax (NaO, 2BrO^{3}) and the microcosmic salt (NaO, NH^{4}O, Po^{5}, Ho).  Charcoal and the platinum wire are used as supports for this kind of operation.