428 



KNOWLEDGE 



[March 17, 1882. 



EASY LESSONS IN BLOWPIPE CHEMISTRY. 



Bv LiKiT..Coi.oNt:L W. A. l{l)^.H, i.atk U.A. 



LtMox IV.— OOKD, SILVKR, 1R0.\, AM) MANGANESE— 



SILICA TIX-MAf;XETKAI, TUEKS. 



THE imrplf niirifcroiiH, or f;<>l<l-l><-&riiiK IhmkI, if now kept Ntoiulily 

 for Home tinir in IIP, hIidwh. through n Imm, niinuU' ii|innt.'li'8 

 of (folil iit'iiin, mill tlipno rc-nrtionH ran Iw n'|M>ntriI by n (fo<xl npcriilor 

 ovor and over ii(f»in. To Hom up the Rold rviic'tiong. Wt> liavr 

 V iioid doinK BH what no otlicr known ocid in clioniislrj- is capable 

 of doinp— dissolving pure gold. We tlien liavo this diasolvod gold 

 canned by the blowpipe to exist in three stales of oxidation in its 

 bead : (ri) ns a tmnsparont, colourless, solution, after n long PI' (a 

 pyroxide which, as wo shall see afterwards, can also bo obtained by 

 trontment on aluniinium plate) ; (b) ns a purple solution, after a 

 half-inch PP ; and (r) as a brownish-" muddy " solution (blue by 

 transniitied light), after OP. Yet wc find it stated in standard 

 works on chemistry Jind metallurgy, that gold is incapable of pvro- 

 logicnl oxidation ! Let ns now trj- in our bead that other desirable 

 metal, ylrrr. If you 8cra|>c, with n penknife, the rim of a sixpence 

 or shilling over n gteet of paper, you get a few specks of silver, 

 nioru tltun sufficient for our purpose; and, perhaps,' her Majesty's 

 Mint will not consider it worth their while to prosecute me for 

 rccuni....nding such an illegal process in the pursuit, or rather 

 sssistsnce, of Knowi.kdoe. These specks are taken up at bottom of 

 the hot P. acid bead, precisely as the piece of gold leaf was ; but a very 

 diilorent result is the con8o<iuence of OP. Instead of the •' muddy" 

 bead in the latter case, the little .silver ball which immediately 

 coheres at the bottom is rajiidly oxidited, and gives out a ([U.-intity 

 of yellow, opaque matter, Uke cream, into the bead, flecked here 

 and there with rod spots and dashes. In fact (to compare small 

 things with great), our P. acid bead now looks, through a lens, 

 something like a liliputian dish of strawberries and cream, with 

 reri/ few strawberries. I will tell you all about the "lens" pre- 

 sently. Our bead is now "argentiferous, "• and the yellow matter 

 (which, I suppose, is pyrophosphate of silver) is rapidly dissolved in 

 this powerful acid, first to an appearance very like that of a thin 

 tortoise-shell comb held agiiinst a window ; then (after a half -inch 

 PP) to a transparent, colourless bead, which vou would never 

 suppose contained silver or anything else. It looks like a drop of 

 pellucid water on the platinum-wire ring. Now, I am going to trj- 

 the mettle of my student. The following reaction, discovered by 

 me in India in 1869, is rather difficult, but onlv requires practice 

 until success attends patience and perseverance. Tlie colourless 

 f,'^"*'^'™"* ^'^^ '^ plunged, but only for a moment, into the 

 " tip " of the blue pyrocone. When drawn out it is found to 

 present a most beautiful and perfect imitation of a pear}. The 

 silver-phosphate just under the surface of the bead has been 

 reduced to the metallic state, and shining like silver through the 

 coating or glazing of phosphoric acid, gives the bead the exact 

 appearance of a pearl. 



The next substance I propose to try BB in P. acid is that honest 

 prop of our native manufactures— iron. I don't think that, on the 

 whole, rust is a dilHcult or expensive thing to obtain in this country, 

 especially when one can afford to keep housemaids ! However that 

 may be, rust is an oxide of iron, containing two parts of metal to 

 three of oxygen, and is. therefore, thus symbolised bv the chemist, 

 Fel O3.+ A considerable quantity of finclv i)owdercd"rust is taken 

 up on the hot P acid bead, and dissolved bv OP ; for it is not a 

 highly colouring oxide like that of cobalt or manganese. The bead 

 IS very soon topaz-ycUow hot, but dissolves a quantity of rust before 

 It retains any colour w hen cool. Kventuallv it looks exactiv like a 

 drop of watery blood; and I thought that if I now dissolved in it 

 by OP a slight trace of MnOj, the bead would assume the bright 

 crimson colour of arterial blood; after HP the dark colour"of 

 venous blood. Chemists have long ago proved that animal (warm) 

 blood contains iron and phosphoric acid, and 1 tried this little ex- 

 periment in order to see if the brilliant crimson colour evidently 

 produced in it by lung-oxidation, might be due to the presence o'f 

 a trace of manganese in the iron of the blood ; I found, however, 

 that the Mn and Fc destroyed each other's colour. 1 now 

 come to try pyrologically, a mineral which is rather too com- 

 mon, especially in the London streets. I refer to mud; or, as it is 

 more politely called, moistened clay, and still more refined by the 

 chemist into the term " Aluminium-sihcate,"! which I shall here 

 shorten to Al. silicate. 



The treatment of Al. silicate in P. Acid PP. affords one of the 

 most important chemical reactions of the latter, because silica is 

 (except (he rare "earth" zirconia) the only substance which is 

 thus insoluble in it. Consequently, w hen we thus treat Al. silicate 



• Latin Ar.ienlnm, silver, and /cro, I bear— silver-bearing! 

 t Pe., short for/(frrum (Ivatin), iron. 

 t (Latin) Aliimrn, clay. 



(or any other silicato) in it, the alumina or other lubstsnce not 

 iiilicn, in at onco diiuolved, and the Kilica left as a cr)-atalline mast, 

 more or less thick in pnij^rtion to the quantity in which it i-xisu 

 in the mineral. The way 1 proceerl is this; — 1 fint diwiolve a xingle 

 S|>eck of cobalt oxide in my P acid bead, which makes it pink. 1 

 then treat in it the finely.jiowderoil mineral, whir'h I suspect con- 

 tains nilicn, and, perhaps, an alkali, as s'lda or potash. 'Tlie silica 

 remains undissolved; the alkali diHsolving, turns the pink bead 

 blue ; alumina in considerable quantity dissolving in absence of 

 alkali, turns the Ixwl mauve colour. Two great lilowpiiie-chemiitj 

 or Pyrologista — Ber/elius (a .Swede) and Plattner (a German) — 

 used the substance called " microcosmic salt," which is practically 

 a phosphate of Sfxlinm, in this way, but the soda of this bead so 

 rapidly dissolves silica as to make its non-solution scarcely any test 

 at all. The whole thing depends np<m the amount of heat applied; 

 and I can dissolve to a colourless transparent bead almost any 

 quantity of Al. silicate in Mic. salt, by simply using u |>owcrfiil 

 blast with my blowpipe. 



Natural oxide of tin(C<M«iferi7<r — Greek, Kaxsiteron, tin)which gene- 

 rally contains a little iron and mans.'anese, may be also usefully 

 treated in P. acid, thus : tin oxide is with difficulty soluble in P. acid, 

 and requires great heat ; iron and manganese oxides, on the contrary, 

 are extremely soluble in it by moderate heat, so that, by holding 

 the bead having cassiterite powder taken upon it in a position 

 where it is affected by a moderate (blowpipe) temperature only, as 

 in a half-inch PP, you obtain the same effect as the chemist does 

 when he uses a dilute acid — that is, you dissolve the Fe. and Mn. 

 oxides, leaving oxide of tin, which can be dissolved out of the bead in 

 nearly a pure state by boiling water, and filtering the solution of 

 iron and manganese. 



I shall now conclude ibis lesson 

 with a description and drawing of an 

 implement (the watch-maker's pliers) 

 mentioned in Lesson II., which I have 

 modified and altered so as to make 

 it answer several pyrological purposes 

 when required ; and these uses are all 

 very mnch, and often, required. I 

 have got an irousuiith of Acton (Mr. 

 Poore) to make me one, from which 

 this sketch is taken ; and very nicely 

 he has made it. He has also promised 

 to make such pliers, and other blow- 

 pipe implements, at a moderate price 

 (I will give it in the next lesson) for 

 poor pyrologists. if required in suffi- 

 cient number ; in fact, I suppose he 

 calls himself a Poore - pyrologist 

 already, for he has been taking 

 measurements of my hot -gas burner, 

 in order to make one for himself. The 

 figure, I think, which is of the natural 

 size, explains itself. The large round 

 legs (apparently, perha]>s. too large, 

 but not so when practically tested) 

 enable the operator, by holding the 

 very tip of a straight platinum wire, 

 held firmly between them from below 

 at the part marked '25, and gently 

 turning the pliers round with his right 

 hand towards his left, which holds the 

 wire, to make a good round ring "25 

 or quarter of an inch in diameter, 

 such as that figured in Lesson II. The 

 Arire is straightened and cleaned (as 

 explained in Lesson II.) by squeezing 

 and dra\ving it gently tluxiogh the 

 broad, fiat part of the legs at A. and 

 I this process is mnch more effectual 



I than that generally recommendc<l by 



j chemists, to dip the red-hot wire in 



hydrochloric acid, which also most 

 certainly rots the wire, and causes it 

 I to break off after a time. 



I The ringed wire is now fixed be- 



tween the legs as far as d (not far- 

 I ther) by drawing up the brass ciJlar 



a to the position shown ; by drawing 

 it down to h, the legs of the pliers are 

 left slightly oi)en, enabling them to 

 pick up small fragments ; by drawing' 

 it to the very bottom e. the legs aro 

 left wide open, and useful for taking 

 uppiecesof charcoal in aluminium-plate operations, &c. The plieis. 



