5'o 



NA rURE 



{_April I, 1886 



are omitted, and the proba'Dility is that the arbitrator 

 would be entitled to assess the value upon profits. 



The second Bill is presented by Lord Houghton as 

 representing the Board of Trade. The print of it has 

 not yet been had, but it is understood to make no change 

 in the objectionable features of the existing Act, but 

 merely to add somewhat to the length of the term before 

 the option of purchase arises. If this be so, it will still 

 leave electric lighting as much "facilitated " as before, for 

 there can be no increase of capital, and therefore no de- 

 velopment, in an undertaking where, in a few years, the 

 enjoyment of the interest upon that capital has come 

 to an end, and where, when it does come to an end, a 

 large portion of that capital will be confiscated. 



Lord Houghton's Bill has this value, however — it 

 shows, first, the length of time it takes the Board of 

 Trade to admit they have made an error, and it shows, 

 secondly, that it requires yet a still longer time to enable 

 them to understand what that error is. 



ELECTRO-DEPOS/TIOX 

 Eh'ctro-depositiou of Gold, Silver, Copper, Nickel, Ss^c. 

 By A. Watt. (London : Crosby Lockwood and Co., 

 1SS6.) 



IN the preface of this book is stated: — "The author's 

 desire was to furnish" "a comprehensive treatise, 

 embodying all the practical processes and improvements 

 which the progress of science has, up to the present time, 

 placed at our command." " The author's aim has been 

 to treat the more scientific portion of the work in such a 

 manner that those who are not deeply versed in science 

 may readily comprehend the chemical and electrical prin- 

 ciples of electrolysis, the knowledge of which is essential to 

 those who would practise the art of electro-deposition with 

 economy and success." How far he has succeeded in 

 his desire and aim, and to what extent the contents of 

 his book are suitable to electro-metallurgists and agree 

 with its title, it is our duty as reviewers carefully to 

 examine. 



The book is essentially and almost exclusively a work- 

 man's manual. In accordance with this we observe that 

 out of about 568 pages, only about 18 are strictly devoted 

 to the fundamental principles or foundation of the 

 subject. 



It 'is evidently written and compiled by a " practical " 

 man who has spent a long period of time in electro-plate 

 workshops. It has various excellences and defects, the 

 most important of which we will endeavour to point out. 

 Its chief excellence consists in the remarkable complete- 

 ness of information given respecting the details of work- 

 shop manipulation, in describing the treatment of nearly 

 every kind of article requiring a coating of electro- 

 deposited metal. The author has with greit industry 

 and perseverance collected a large amount of such infor- 

 mation, and his book is especially full of details respect- 

 ing the electroplating of articles with nickel. The 

 information contained in it is, with certain exceptions, 

 well up to date, and the printer's errors are remarkably 

 few. It has also the advantage of a copious index con- 

 sisting of nearly 50 pp., and the subject-matter of the 

 book is conveniently divided into chapters of moderate 



length, with the contents of each chief paragraph plainly 

 indicated by bold headings. 



Its greatest defects are those of omission ; it is seriously 

 deficient in the chemical, chemico-electric {i.e. voltaic), 

 and electro-chemical {i.e. electrolytic) principles of the 

 subject. Throughout the volume nothing is said respect- 

 ing the fundamentally important matter, both theoretically 

 and practically, of the chemical valency of the elementary 

 substances ; the chemical, voltaic, and electrolytic equi- 

 valents of those elements are also neither given nor 

 explained. On p. 513 a table of atomic weights of the 

 chemical elements appears, but as only a portion of these 

 are equivalent to each other, and those not indicated, 

 they would, without the valencies or a separate table of 

 combining-proportions, in many cases only mislead an 

 unscientific workman. The only indication of any differ- 

 ence existing between atomic-weight and chemical-equi- 

 valent is contained in a footnote to that table, saying, 

 " the combining-weight of oxygen is 8." 



From beginning to end of the book, the molecular and 

 equivalent weights of all the compound substances em- 

 ployed in electro-deposition are omitted ; none are given 

 even for the commonest substances, such as sulphuric 

 acid, potash, soda, lime, double cyanide of silver and 

 potassium, blue-vitriol, potassic cyanide, double sulphate 

 of nickel and ammonium, &c. ; similar remarks may be 

 made respecting the salts of zinc, cadmium, lead, tin, 

 iron, nickel, copper, silver, gold, palladium, platinum, 

 bismuth, antimony, &c. ; also respecting hydrochloric, 

 nitric, and other acids. Almost the only exception 

 appears to be on p. 4S3, where it is said, respecting the 

 salt used for making nickel-plating solution: — "The 

 double salt consists of i atom of sulphate of nickel, I atom 

 of sulphate of ammonium, and 8 of water." 



Throughout the book also the chemical formute of all 

 those compounds are omitted, notwithstanding that they 

 would enable the workman to arrive in many cases at the 

 chemical equivalents by comparing them with the atomic 

 weights, and would also assist him to more perfectly 

 realise and remember the actual chemical composition of 

 the acids, bases, and salts used in his occupation. 



In accordance with these omissions, no principle or 

 general rule is supplied which will enable the operator to 

 calculate how much in weight of a given metal or base 

 would be necessary to neutralise a known amount of a 

 particular acid, nor what quantities of acid and base 

 would be required to form a certain weight of a salt, in 

 m.aking and correcting his various solutions ; nor how 

 much current would be generated by the consumption of 

 known amounts of different positive metals or of different 

 acids ; nor what quantities of different metals would be 

 deposited at the cathode, or of unlike ones dissolved at 

 the anode, by the passage of a given amount of current 

 through an electrolyte. Respecting this latter point, on 

 p. 72 it is, how-ever, stated : — " The decomposing effects 

 produced by the voltaic current in different electrolytes 

 are precisely in accordance with the atomic-weights or 

 cliemical-equivalents (which see) of the substances elec- 

 trolysed." " For example, the same amount of electricity 

 that would reduce 56 parts of iron from its solution to the 

 metallic state, would reduce 207 parts of lead or 108 of 

 silver." But the " chemical-equivalents " to which the 

 reader is here referred are not to be seen in the book, 



