Page:Popular Science Monthly Volume 49.djvu/716

694 The second of Dr. Dana's published writings was issued in 1833, while he was on a visit to England. It was a clear exposition of the chemical changes occurring in the manufacture of sulphuric acid.

In the following year Dr. Dana became resident and consulting chemist to the Merrimac Manufacturing Company at Lowell, Mass., in which position he remained for the rest of his life—a period of thirty-four years. The improvements which he introduced into the processes carried on in the mills of this company were many and important. Dr. Hayes gives an outline of these. He undertook systematic researches on the action of the dung of beeves—then used for removing the excess of mordant in printing calicoes with madder—which resulted in the discovery that crude phosphates in a bath with bran are a complete substitute for the expensive and disgusting material before deemed indispensable. Arseniates, which are cheaper than phosphates, were afterward substituted for them on the suggestion of Mercer, and are the world-wide reliance of print manufacturers at the present day.

Of the same systematic character was his study of the chemical changes involved in the process of bleaching cotton fabrics preparatory to printing them. This inquiry resulted in his inventing a method which not only received high commendation as scientific work but was universally adopted in practice. As most of Dr. Dana's researches were made for the exclusive benefit of the company with which he was connected, their results were not always published promptly, and hence the abilities that might have won a high meed of fame remained known to only a small circle. His discoveries with respect to bleaching cotton, however, were published in the Bulletin de la Société Industrielle de Mulhouse in 1838. The principles therein established have led to the American method of bleaching, of which Persez, in his Traité de l'Impression des Tissus, says that "it realizes the perfection of chemical operations."

The Merrimac Mills were at first run by water power alone, but when the works were extended this was supplemented by the use of steam. Dr. Dana was now called to the new field of engineering, in addition to his other duties. His development of the whole subject of the evaporative power of coal and the economical disposition of the heat in steam and in water of condensation is a masterly effort, embracing every detail, and was in advance of any published results of the time.

For several years before he became a resident of Lowell, Dr. Dana was frequently called to that city as a consulting chemist. He was also one of the chemists consulted by the water commissioners of both Boston and New York prior to the introduction of the Cochituate and Croton water respectively.