Analysis

Analysis, Chemical. The operations which are necessary to ascertain the chemical structure of substances come under the head of chemical analysis. If we require to know only what substances are present, irrespective of quantity, the analysis is called qualitative. Thus, to prove the atmosphere consisted of nitrogen and oxygen a qualitative analysis alone would be necessary. If, however, we further require to know how much nitrogen and how much oxygen, a quantitative analysis is requisite.

Quantitative analysis is usually subdivided into Gravimetric and Volumetric; gravimetric, or weight-analysis, being characterised by the use of the balance; and volumetric analysis by the use of graduated vessels for the careful observation of volumes.

Analysis is also termed Inorganic or Organic, according to the nature of the substance under inquiry; and organic analysis is furthermore itself divided into Ultimate and Proximate, according as we attempt to discover the ultimate elements which are present, or those groups of elements which are known as proximate principles.

In the case of complex organic substances an ultimate analysis is often quite useless. With blood, for instance, it would be meaningless to ascertain how much carbon, hydrogen, and oxygen were present; it is first necessary, by the methods of proximate analysis, to split the blood up into albumin, fibrin, fat, haemoglobin, mineral salts, etc. We may then apply the methods of ultimate analysis to these isolated individual substances if we will.