NOTU ON CAMPHOR MP,TlONS.
13
of silver, the lowefit limit, to 60 melts, thc higher limit, in a single crucible. I h w e no doubt that a careful study of the prmciples crf the manufacture of black lead crucibles here developed, somewhat fully, and even perchance their farther development, beyond my conception, can improve their quality R O as to double the life and strength ascribed to t h u n . u. s. ~ I I S T , PHILADELPHIA, Dec. 31, 1864.
NOTE ON CAMPHOR MOTIONS. BY P. CASAMAJOP.. On the 4th of October, 18’17, I read a paper “ O n the Motions of Camphor on tlic Surface of Water,” before the American Chemical Society, in wliicli I described experiments, which had led me to the conclusim that these motions were due to electricity. The extraordinnry motions which give an appearance of life to pieces of catnphor, swimming on the surface of water, are not to be seen at all times. Very often camphor will remain motionless, while at other times the pieces gyrate with great animation. One of the earliest observers of these singular motions, Itomien (1748), came to the conclusion that they were due to electricity, while subsequent investigators, among whom may be counted the great Volta, have generally decided that there is no connection between electricity and the motion of camphor on water. I w a s led to believe that camphor motions were due to electricity by the results of experiments, of which I will give a brief account. When pieces of camphor are thrown on water, they may remain torpid or they may gyrate with every appearance of life. I n the latter case, the motions may be instantly arrested by dipping a finger in the water on which the camphor moves. If we have pieces of camphor lying quietly on water, they may be made to move by dipping into the water a rod of either glass, sealing wax or rulcanite, electrified by friction. After every immersion. the glass is to be dried by wiping with a dry cloth or a piece of bibulous paper ; And, hefore every immersion, the rod is electrified by rubbing with a piece af silk or flannel. After one or more immersions of the electrified rod, the camphor motions invariably start, and by a fow additional immersions they increase in intensity. T h e fact that .these
11
S O l E O N C A M P H O R MOTIONS.
Inotioris coitld be started by means of an electrified rod was a new one. Those who had decided that camphor motions were nc~tdue to electikity were not acquainted with it, and I was led to believe by this fact, and by othcrs which I gave a t the time, t h a t caniphor motions were rlcdrical phenomena. There was, however, sornetliing uiisat isfactory in this method of applying electricity to the wateron wl~iclipiecesof camphor floated, but, at that time, no other methotl occurred to. me. Aftei*ward.: t'he whole siiklject slipped from my mind, but, quite recently, tiit' following experiment Iias suggested itself, which seems to sliow that carnplior motions art' iiot due to the state oi' electrical tension of the liqnid on wliicli pieccs of c:iniplior float. Tlie espeiiiiicfiiit waa performed in R glms dish about t w o inches deep, and of five inches diameter. 'l'his was fillet1 with water up to within an inch of the tup. The bottom of the dish and t h e sides, iip to within ail inch of the top, were covered with tin foil. A metallic wiw dipped in the water of tlie tlish, with one end 'oiit of thc water, b u t having no coiiiiectioii with the outside lining of tin foil. 1liis glass dish wis the equivalent of a T~aydenjar, which C(J11ld be charged with electricity t'roin the plate of an electropliorus by touchiiig tlic wire iiil'piilg into the w t t e r with this plat(,, laying :i tinger ; r t tlic saiiie time on the outside aimiature. A few pieces of camphor were placed upon the water in the dish, ant1 these were reduct~dt o immobility by dipping a finger in the water. After this tlic w:itcr in t h e dish wa' charged with tilevtricity by repeatedly plaoirig the plate of an electrophorus in t o n t a c t with tiit. ir.irc, diplling into I h e water, irliilc tlir outridc, armatlire was touched w i t h a tinger. Thcre was no effect produced on the pieces of carnplior floating on the water of the dish. These reiiiaiiied motionless, not exhibiting the sliglitest tremor. There ooiild be no doubt that the water surfiice w i s in a greater state of electrival tension in this experimeiit tliaii when the water is electrified by clipping an cxciteti rod in i t , for, by placing one liand on the ontside armature of the dish, and slowly approaching the water surface with a finger of the other hand, a perceptible spark was obtained. There sccms to be :t di.crepancy between the results t o be obtained in these two classes of exlieriments. r ,
NOTE ON CAYl’LIOR MOTIONS.
15
By dipping an electrified rod Ruccessively in water the oamphor motions always take ?lace, while, when wo electrify by applying t h e plate of an electrophorus t o the water in the dish, as described, not the least tremor can be perceived. As these resnlts were obtained over and over again, there cannot be any doitbt as to the difference of the effects in the two modes of operating. The conclusion that may be drawn is that camphor motions are not caused b y electricity. In the case of an electrified rod, dipped successively in water, I am inclined to the opinion that electricity acts illdirectly by removing physical impurities from t h c surface of the water, x ~ eshown by the following experiment : Take a glass of water, and on its snrface p1:ice a few pieces of camphoi-. If these are inclined to move, they may he stopped by dipping a finger in the water. ‘l‘hen blow a cloud of lycopodium powder over the 8urfac.e of the water, PO as to covw this surface iiniformly with the powder. If now an eleetritied rod is clipped repeatedly in the water, wiping it dry ltfter every immersion, and, rnbbiiig it with a piece of tlaiinel before dipping in the water again, the result will be that the pieces of camphor will move ar if gifted with life. It will be noticed a t the same time that the surface of the water will be almost entirely free from lycopodiiim, as the powder has been gradually removed b y each successive immersion of the electrified rod, which attracts lycopoilium like nll other light bodies. If now we suppose that 6lms of oily matter are removed in the same way b y an electrified rod, we may ronccive how electricity can act indirectly in i emoving impurities from the burface of the water. There would remain to explain why films of oily matter or other inipurities act as a check oil camphor motioiis while a phqsically clean water surface 1s a favorable condition in pi oilucing these motions. Towards the solution of thcse questions I will venture the following explanation, which may serve as t h e base of further reNeal-clies. It is a well ascertained fact relating t o camphor motions, that when these motions take place the camphor dissolves in water more quickly than when the camphor is a t rest. I think t h a t a cunnection exists between camphor motions and the three following facts : let, that camphor dissolves in water quite easily at times ; 2d,
16
O X TIlE METHODS
OF 1SI)IGO TESTIN(:.
that its density allows it to float on water ; and :3d, that the solution has a density slightlp different from t h t of water. I am riot prepared a t present to develop these ideas, whirli would requirc. further experiments to establish. I will confine myself to the well ascertained fact that ;L piece o r camphor wears away much fasier wlien iii motiori than when at rest. This being established, it appears more thaii probable that if a piece of camphor is perfectly free 1‘roiu oily matter it will dissolve i n water more readily than if protected hy a greasy film. The slightest film of this nature, iii contact with campilor, becomes :i saturated oily solution of camphor, and if m y exc what will cover the camphor, the qreasy film will Extend over t,he surl‘ace (If t l i r watcr. TVlien tliings are in this miidition, if an electritietl rod is ciil)petl several times i n the water, every immersion w i l l i*eiiiove x portioii of oily film froin the surface, until finally t h e film O I I each piece of‘ camphor becomes so tliiii that tlie water rc?nc.lies the. iiicccs of caniphor, and tliesc immediatc.ly bworce gifted with inotioii. OS THE NETHODS OF ISIjIGO Tli:S’I’ISG. BY 1 1 E s 1 t - r l r . RAC.i’ll. 11. I r appears s t r m p e , wlien the higli pi,icc of‘ iritligo and its large consumption i n the industrial arts :irv conaitlci.cd, that the methods commonly cinpIoyc(1 in this coiiritry f o r ils i.:i!untion should, from a scientific standpoirit, be so c . ~ ~ i d:ind e inaccurate. Taking t h e a ~ c w g epricc of tliv v:irious gr:i(les of indigo in the iiinrket as a h i s f o r vnlculatioii, it niay be stated tli:it a single per cent. of iiidigotiiie rcprcsentr, t o t I i v wnsuiii(’1’. from t w o to t,n-o and one-half cents for each pouiiil o f good.: ~iut~c*liascd. Under these c,ircunistances it n-oiihl seer11 highly i1c:siixble to ernploy t c s t s as acciirate as possible, evcw tliough tlitB>e should not hi. as time-saving as the grenter niinihhr of wninicLrcia1 tests. Nevertlielt~s\,it is :i fact, t h a t t h e ordinary iiidigo “:inalyscs” are YO wide of reliable results, that giitw work niiplit quite tis well br substituted for t h e m , and this in face of the I‘:ict tli:it ,TVC have in the gmvimctric determination b y tlic reduction methods, a means for a closer valuation of indigo tlimi can b e applied in the case of almost any other dyestuff.
