Aggregation

Aggregation. Many substances are capable of existing in the three forms of matter - solid, liquid, and gaseous; and the difference between them in these diverse conditions is supposed to consist in the distances which exist between their ultimate molecules. Again, many substances are identical in chemical composition and in physical state, but entirely different in their physical properties, and here, again, the difference is due to the dissimilar ways in which the same elementary molecules are aggregated. An excellent clue to the laws of aggregation will doubtless often be furnished by a study of colour changes.