As heretofore, I beg to solicit my readers to apprise me of any inaccuracies or omissions in this volume which may come beneath their notice. I shall also thankfully receive any hints or suggestions tending to the improvement of future editions of this work. Such communications, to be useful, must, however be written on only one side of the paper. Parties who may thus kindly afford me assistance will, in due course, have their services publicly acknowledged; and their names and addresses, unless when otherwise requested, will be published in full. I have endeavoured to render the present volume as self-explanatory as possible, and, in general, have appended ample directions to the several formulæ and processes that seemed to me likely to cause embarrassment to those inexpert in chemical manipulation; but should any party find it otherwise, I shall be happy to reply, gratuitously, to any reasonable questions tending to elucidate the difficulty. In conclusion, I may add that, having now for nearly a quarter of a century devoted my attention to the applications of chemistry in most of the useful arts and manufactures, both British and foreign, and in sanitation, I am in possession of many valuable processes and formulæ, hitherto wholly unknown, or but partially developed, with various improved plans of factories, laboratories, ventilation, &c., which the limits of this work will not permit me to describe in its pages, but on which I should be happy to communicate with parties interested in the same. Persons desirous of establishing any new branch of manufacture, or of improving an existing one, or of determining the purity or value of articles of food, wines, liqueurs, medicines, &c., or of obtaining formulæ or processes which are not contained in this work, may, in like manner, have their wishes complied with, by enclosing to me samples, or the requisite information. ARNOLD J. COOLEY. NAMES OF THOSE WHO HAVE CONTRIBUTED TO, OR ASSISTED IN THE REVISION OF, THIS EDITION JOHN ATTFIELD, Ph.D., F.I.C., F.C.S., Professor of Practical Chemistry to the Pharmaceutical Society of Great Britain. J. WORTLEY AXE, P.C.V.M.S., Professor of Histology in the Royal Veterinary College. LLOYD BULLOCK, F.I.C., F.C.S. E. L. BARRET, B.Sc., F.I.C., F.C.S. E. CANTON, F.R.C.S., Surgeon to Charing Cross Hospital. SPENCER COBBOLD, M.D., F.R.S., Professor of Parasitology and Botany in the Royal Veterinary College. STEPHEN DARBY, F.C.S. DR DE VRIJ, of the Hague. JOHN GARDNER, F.I.C., F.C.S. WILLIAM HARKNESS, F.I.C., F.C.S., F.R.M.S., Assistant Chemist in the Laboratory of the Inland Revenue Department, Somerset House. C. W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the Charing Cross Hospital. EDMUND NEISON, F.I.C., F.C.S.