li'S 



UNDULATORY FORCES. ELECTRO-METALLURGY. [GENERAL PRINCIPLES. 



because, after all, its success de^-nds on can-fill manipu- 

 lation ; fur with ever so perfect :i knowledge of principles, 

 without a perfect knowledge of the application of those 

 principles in the form of practical rules anil manipula- 

 tion, success cannot possibly be attainc<l. \Vith the 

 i-iul in view, we shall avoid saying anything about the 

 history of the subject, or the t-liiiins of rival disco vcron 

 or inventors these U-ing subjects for the historian, 

 hall wo say much about the electro-deposition 

 of rare metals, or about any collateral branches of the 

 subject, cxi-eptin;,' only so far as they are capable of 

 illustrating the subject in a direct manner, or of other- 

 wise furtherim; the object in view. 



To enable the reader to master the subject as he pro- 

 ceeds, we have so arranged it that every portion shall be, 

 so far as it goes, complete in itself, requiring no anti.-i- 

 patory knowledge of more advanced parts to enable him 

 to understand it. 



The only arrangement which admits of this important 

 object being attained, is to explain the theory before 

 treating of the practice, and by arranging the theory in 

 an iiuluctire order. In other words, we shall commence 

 with the. variims classes of facts on which electro-deposi- 

 tion is founded, and ascend from these to the general 

 laws or principles, chemical or electrical, which govern 

 them. Proceeding from the theory to the practice, ar- 

 rangiii',' all in a dnhtclire order, and applying theoretical 

 principles in the form of practical rules, the results can- 

 not be other than successful. Beginning with the more 

 general rules v/hich apply to all electro-deposition pro- 

 oesses, and to the electro-deposition of all metals, and 

 proceeding, step by step, to those more special rules of 

 manipulation which are required for tlio working of par- 

 ticular metals and solutions, the necessary requirements 

 for the production of the more difficult substances and 

 more complicated works of art will be attained. Through 

 the whole chapter, the reader will thus be led gradually 

 from the most common and well-known facts, to the mo&t 

 complex and difficult applications of electro-deposition. 



In accordance with this plan, the subject will com- 

 mence with a review of such facts of electro-deposition as 

 every man possessing the few necessary materials', which 

 are easily procurable, may readily verify for himself. On 

 these facts the whole subject throughout will be based. 

 From them we shall proceed to the circumstances or 

 mndit inn* under which they occur; namely, the causes of 

 electro-deposition. The principles will be inferred from 

 the facts as we proceed, until we arrive at the more ab- 

 stract laws of the phenomena. 



The facts will be based on numerous experiments, in 

 which instances where deposition does occur, as well as 

 experiments in which it does not occur, will be cited. 

 These investigations will satisfy the reader, that in all 

 where deposition does occur, certain conditions are 

 invariably present ; and where it does not occur, one or 

 more of them is invariably absent ; and, therefore, that 

 the conditions observed are essential to the production 

 of the phenomena. Another and more ultimate reason 

 for mentioning negative as well as positive instances is, 

 that, in practical working, it is nearly as important to 

 know what will prevent deposition, as to know what will 

 produce it. 



The following table exhibits the phenomena of electro- 

 dcposition, arranged in an inductive order, suitable for 

 teaching the sill >y, and ithout immediate 



reference to its practical applications. The first portion 

 10 table contains the facts of electro-deposition, 

 divided into seven dMMI, under which may be ranged 

 the whole known facts of the art. The second portion 

 contains the princifdc* or conditions under which those 

 facts are manifested; thews are also divided int<> 

 classes, which are capable of including all the known 

 conditions or causes of electro-deposition. 



A. FACTS. 



1. Deposition by one metal and one liquid 



2. Deposition by two t.ils and liquid. 



3. Deposition by one metal and two liquids. 



4. Deposition by two metals and two liquids. 



5. Deposition by connecting either of the foregoing | 



.ments (except the first) with a separate depositing 



liquid. 



ti. Deposition by connect in:; other sources of depositing 

 power with a separate depositing liquid. 



7. Deposition by combinations of the foregoing. 



B. PRINCIPLES. 



1. Chemical conditions of deposition. 



2. Electrical conditions of deposition. 



3. Thermal conditions of deposition. 



4. Mechanical conditions of deposition. 



6. Mathematical conditions of deposition. 

 C. Logical conditions of deposition. 



7. Ontologies! conditions of deposition. 



This arrangement has been used with much success in 

 teaching the theoretical part of electro-deposition, as it 

 enabled the pupils to understand each portion clearly as 

 they proceeded. The plan adopted was 



First, to exhibit before the pupils numerous experi- 

 ments of each class of facts in succession, including 

 positive cases in which deposition did occur, as well as 

 negative ones in which it did not occur. 



Second, to place each of the theoretical principles in 

 succession before them in the form of a hypothetical 

 question, referring them to the various facts on which it 

 is founded, and leaving them to observe for themselves 

 whether or not the principle there stated was borne out, 

 allowing them to draw their own conclusions. By this 

 method they were soon led to observe, that, wherever 

 deposition occurred, certain conditions were present, and 

 that where it did not occur those conditions were absent. 



When treating of the laws and principles of deposition, 

 the reader will be referred back to the facts upon which 

 they are based ; so, when describing its practical appli- 

 cations, ho will in like manner bo referred to the laws or 

 principles for his guidance : his knowledge of the practice 

 will thus be based in a great measure upon the principles, 

 as the principles will be deduced from the facts, which, 

 as we have said before, are within the reach of every one 

 to repeat and prove for himself. 



The practical part will treat, in succession, of tho 

 general rules for working all the different processes of 

 washing or dipping, whether by single cell, battery, or 

 other process. The requisites for preparing good de- 

 positing solutions, both for simple metals and alloys, 

 with methods of making solutions generally, and of 

 working them ; suitable sources of electricity, either by 

 the magneto-electric machine or other batteries, together 

 with their construction ; as well as instructions for 

 regulating the quantity and intensity of the current; 

 regulating the quantity and quality of the deposited 

 metal i cleaning and preparing metallic surfaces for re- 

 ceiving adhesive and non-adhesive deposits; copying 

 works of art in various substances; elastic moulding; 

 preparation of non-conducting surfaces to receive a 

 deposit; multiplication of works of art by deposition; 

 deposition, by the various processes, of such metals and 

 their alloys, as antimony, bismuth, zinc, cadmium, tin, 

 lead, iron, cobalt, nickel, copper, brass, German silver, 

 mercury, silver, gold, platina, and palladium ; chemical 

 relations of the cyanides of gold and silver ; manufacture 

 of cyanide of potassium ; recovery of gold and silver 

 from damaged solutions ; and a full list of patents upon 

 electro-deposition will be fully treated on as we proceed. 



THEORETICAL DIVISION OF THE SUBJECT. 



1. Facts. One Metal in One Liquid. There are various 

 modes in which deposition of one metal 

 upon another may take place; and they 

 may be classed as follows : 



1st. By the simple immersion of one 

 in "ii.i liquid (Fig fill); namely, by 

 putting the metal to be coated into a 

 .solution of the metal to be deposited, and 

 allowing it to remain a longer or shorter 

 period of time, the liquid being at a 

 suitable temperature ; for instance, if wo immersa a pieco 



