244 



ELEOTEICITY. 



Warren De la Rue, in remarking upon the 

 ingenuity displayed in the construction of the 

 apparatus, suggested that, while it would be 

 found serviceable in electro-plating and other 

 applications where a somewhat intense current 

 was employed, he doubted its use in the ordi- 

 nary electrotype process for the deposition of 

 copper, where weak currents only were re- 

 quired. 



A New Exciting Liquid. In a note to the 

 French Academy of Science, M. Delaurier men- 

 tions a new exciting liquid for galvanic batter- 

 ies. He says that, in order to obtain very pow- 

 erful batteries disengaging no deleterious gas, 

 and of very cheap maintenance, he has solved 

 the problem of transforming azotic acid into 

 sulphate of ammonia, under the influence of 

 sulphuric acid and hydrogen. This he does by 

 the agency of protosulphate of iron ; the pro- 

 portions are twenty parts of the protosulphate 

 dissolved in thirty-six parts of water (the op- 

 eration being sheltered from contact with the 

 air), to which are added, with stirring, seven 

 parts of diluted (equal parts) sulphuric acid, and 

 then hi the same manner one part of diluted 

 (equal parts) azotic acid. He says that the re- 

 sulting liquid is the most energetic and most 

 economical that he knows for an exciting 

 liquid for iron, zinc, and other metals without 

 any disengagement of hydrogen or binoxide of 

 azote. In the use of this liquid with nitric 

 acid in Bunsen's pile, the action goes on with- 

 out any exterior emanation of nitrous gas, and 

 without the emission of hydrogen in the inte- 

 rior, and consequently the platinum does not 

 polarize. 



Decomposing Action of the Voltaic Arc on 

 Certain Substances. Mr. F. P. Le Koux, in a 

 paper in the London Chemical News, offers evi- 

 dence to show that the earthy and alkaline- 

 earthy oxides undergo a real decomposition 

 in the voltaic arc. If a cylinder of magnesia, 

 or lime, or strontia, be fixed in the voltaic arc, a 

 slight cavity instantly forms at the base, and 

 the conditions remain the same for an indef- 

 inite time; the arc continuing to play upon the 

 body without inducing any change but the vitri- 

 fication caused by the siliceous vapors emitted 

 by the impure charcoal. If, however, the cyl- 

 inder of earthy matter be brought into actual 

 contact with the charcoal points and the press- 

 ure maintained with a slight spring, different 

 results follow. If a pencil of lime, or even 

 plain chalk, be used, the carbons wUl hollow 

 out in it a sort of trench in which the heat is 

 condensed as in a sort of reverberatory furnace, 

 and the amount of light emitted is proportion- 

 ally augmented. On examining the light with 

 a piece of black glass it presents the appearance 

 of an opaque luminous cloud in which the ex- 

 treme ends of the charcoal are undistinguish- 

 able, their usually well-marked brilliancy be- 

 ing lost in the mass of light, and there is a 

 sensible evolution of whitish fumes. The spec- 

 troscope displays an intermittent spectrum filled 

 with large and brilliant rays, which are recog- 



nizable as those described by different authors 

 as characteristic of calcium, but their number 

 and intensity is greater and they are better de- 

 fined. This is not surprising if the difference 

 between the luminous intensity attainable by 

 this process and by those hitherto employed 

 be considered. It would be doubtless possible 

 by this method to obtain much new informa- 

 tion respecting the spectra of metals, provided 

 only pure products were employed. 



The employment of strontia gives analogous 

 effects under the same conditions, the light as- 

 sumes a characteristic red tinge, and the spec- 

 troscope displays the rays characteristic of 

 strontium, thus presenting a simple means of 

 enriching the electric light with red rays. It 

 may be here remarked that the flame always 

 contains a large proportion of white light, for 

 if the metal be set free in some parts of the 

 flame, in others it returns to the state of oxide, 

 the incandescence of which always yields a 

 white light. 



Color-effects of Electric Discharges. The 

 American Journal of Science for May, 1868, 

 contains the substance of a paper, read by M. 

 Becquerel before the French Academy, on the 

 effect of coloration presented by discharges 

 from an inductorium taking place between the 

 platinum wire and the surface of a liquid. The 

 apparatus employed by the author was very 

 simple, consisting merely of a glass tube, part- 

 ly filled with a saline solution in contact with 

 a platinum wire forming one pole of an induc- 

 torium. The other pole was formed by a pla- 

 tinum wire, the extremity of which was placed 

 a few millimetres above the surface of the 

 Jiquid, the discharge taking place between the 

 liquid and the wire. In case the inductorium is 

 of low power, coloration is not observed when 

 the liquid is positive and the wire negative, but 

 only when the wire is positive. But when the 

 coil is powerful, and the salt dissolved easily 

 vaporized, coloration is observed in either case, 

 though the maximum is given when the wire 

 is positive. With a sufficiently powerful coil, 

 the luminous effects of the discharge are very 

 brilliant. The spectrum of the light produced 

 in this manner is more complex than that re- 

 sulting from the introduction of small quanti- 

 ties of saline matter into a non-luminous flame. 

 The water is vaporized and we have lines due 

 to oxygen and hydrogen ; the temperature is 

 also higher than that of the flame of a Bunsen's 

 burner. With very pure water the intensity 

 of the discharge is feeble and the spectrum con- 

 tains the red and blue hydrogen line corre- 

 sponding to the dark rays and F of the solar 

 spectrum. With a strong solution of chloro- 

 hydric acid in water the tint of the discharge 

 is slightly violet and the two red and blue rays 

 are more distinct than with water. There are 

 also an orange band and a few fainter rays 

 throughout the extent of the spectrum. A very 

 small quantity of saline substance in water is 

 sufficient to communicate to the light of the 

 discharge the color due to the elements of the 



