Feb. 24, 1882.] 



KNOWLEDGE ♦ 



359 



EASY LESSONS IN BLOWPIPE CHEMISTRY. 



By LiEiT.-CouixEL W. A. Ross, late R.A. 



Lesson m.— MANGANESE— COBALT— GOLD. 



(Note Introductory.) 



I SEE yonr typographical demon has promoted me into the Boyal 

 Navy (one of the best pyrologists I know is a Captain R.N.), 

 and should think the printer's other inference, that the rank of 

 colonel has been lately created in the English navy, is also a mis- 

 taken one. — Erratum in Lesson 1. It should be stated that the 

 two " body tubes " of the blowpipe are " two 6-inch pieces " — not 

 "2 in. pieces." In Lesson II., (1) the firm in Hatton-garden is 

 "Johnson & Matihey," >it-( "Johnson i Mather." (2) Frciberg is 

 wrongly spelled with a «, not by me ! 



I hope some of my sharper pupils, having tried the experi- 

 ment with oxide of manganese, detailed in Lesson II., will 

 find out that I have omitted to mention a very remarkable 

 " reaction " (which is the chemical term for a phenomenon 

 depending npon tho application of any particular operation). 

 It is thus : — On first heating the manganese (brown) oxide* 

 with the phosphoric acid, great effervescence, or bubbling, 

 takes place, and the bubbles are tinged a deep crimson colour. 

 This extremely delicate reaction will detect 005 of manganese in 

 minerals or compounds. The phenomenon described in the tinal 

 paragraph of Lesson II. is evidently the result of holding the bead 

 (on platinum \vire) in two different positions as regards tho blue, 

 blo\vpipe-pjTocone. In any position (o) in front of the " tip or 

 point of the blue," as it is called, the manganiferous bead assumes 

 an "amethyst," or bluish-violet colour; in any position within the 

 blue, the bead becomes colourless (b). 



Position (a) is called in most blowpipe books " the oxidating 

 flame," or briefly, OF. Position (b) " the reducing flame," or RP. 

 I have altered these names in my books, because they do not cor- 

 rectly describe the resulting reactions. In the first place, there is 

 no '■ flame" at all, but, instead, a cone of non-luminous, blue fire ; 

 secondly, many beads (an auriferous, or gold-bearing bead, for 

 instance), so far from being oxidised just in front of the blue tij), 

 suffer a deoxidising or " reducing" process, whilst the position (h) 

 does not invariably reduce all substances dissolved in these beads — 

 oxide of chromium, for instance — and produces many phenomena 

 besides reduction, as that of "colouration," " precipitation," &c.t 



1 have therefore, thought it better to describe these important 

 situations of the subject of analysis by symbols expressing the 

 na(i!/eof the fire which, in that position, attacks it, thus: — HP 

 (instead of RF) for hydrocarbonous J pyrocone; OP (instead of 

 OF) for oxjhydrogen pyrocone, and PP (no old name), for 

 peroxidising pyrocone. This last position extends from i in. to 



2 in., or even 3 in. — if the blast is sufficiently strong — in front of 

 the " blue tip." Let us now revert to our phosphoric, mangani- 

 ferous § bead (these are rather long words, but necessarj-, and 

 easily learned and remembered by the r^al student). Chemists 

 have ascertained that the common or brown oxide of manganese 

 contains two proportions or parts of oxygen to one of the metal 

 manganese. Tlieir symbol for manganese is Mn, and they, there- 

 fore, symbolise this compound thus : MnOj. They have also found 

 that the " red," or violet oxide contains the proportion three of 

 metal to four of oxygen, and have thus S}TnboIised it lln304. 



The chemical action of the different parts of the blowpipe pyro- 

 cone, therefore, is admirably illustrated by the Mn. bead ; for, as wo 

 have seen, the relative proportions of metal and oxygen of the com- 

 pound dissolved in it are actiiallj- and materially altered by a simple 

 movement of the hand '. The lowest — that is, the nearest metal — 

 known oxide of manganese, is what chemists call the " monoxide," || 

 MnO (obtained by heating the common carbonate in a gun-barrel, 

 through which hydrogen gas is pa.=sed), and is a green powder; 

 what oxide, therefore, tho cohurless bead after treatment in HP, 

 contains, is not yet, apparently, known. 



* Oxygen (acid generating). — A gas discovered by an Englishman 

 (Priestley) in Birmingham in 1772. It is a component of almost 

 all natural inorganic substances. 



+ Precipitation (a falUng down) is the condition when a bead 

 becomes "muddy" or opalescent, which before was transparent, 

 or " clear." The oxide, or substance which before was dissolved 

 in the clear bead, has, by some act, become insoluble, and is 

 "precipitated." 



J Hydrogen (water generator), a gas ; with oxygen forms water, 

 and in that form is a constituent of almost all substances, organic 

 and inorganic. It is also with carbon, a component of oils, fats, 

 4c., which arc called " hydro-carbons," and therefore, of the ignited 

 gases proceeding from them when burned. 



§ Manganiferous. — Bearing (or containing) manganese. 



II Honoxide. — Greek Monos one, and oxide. 



One of the greatest chemists that ever lived, in days when great 

 chemists did not despise the blowpipe, discovered this curious re- 

 action of manganese in borax. His name was Scheelo. He was at 

 first only an apothecary at Koping, in Sweden. 



I am now going to ask my student to make another " bead," still 

 prettier than the last, by means of a substance almost as cheap as 

 manganese, and he shotild go to the same place for it — viz., to the 

 glass-works ; I mean oxide of cobalt. The minerals in which cobalt 

 was first found in Germany were so like silver, that when the miners 

 found they did not contain silver, they said they must have been 

 silver changed in character, or be-devilled by some demon, and 

 Kobold is the German for demon. 



The phosphoric acid, or, in brief, P. acid-bead, is tinged with 

 cobalt oxide, or CoO, in the same manner as the former one was 

 with MnO.. (see Lesson II.), but see what a different result we have 

 got ! This bead is blue hot, but in cooling assumes a magnificent 

 \noIet colour. It is not altered in appeai'ance by holding it in ttie 

 positions OP, or HP, or PP — all cause it to be bine hot and \-iolct 

 cold. In all blowpipe tables and books (except mine), yon will see 

 " blue " only set against cobalt; but in 18C9 I discovered that P. 

 acid gives this beautiful colour with cobalt, and thought that by 

 adding a weighed quantity of soda to the bead before the blowpipe 

 (or briefly, BB) until it remains blue cold, I should obtain a kind of 

 measure for the soda added ; and, as the bead is thus made blue by 

 any alkaU — an alkalimeter,* or alkali-measurer ; and this is the 

 fact. You can also measure the quantity of cobalt in minerals, Ac, 

 in this way, and in my little book, " An Alphabetical Manual of 

 Blowpipe Analysis," pp. 45 to 18, is given " A Blowpipe Assay of 

 Ores, Furnace Products, &c., for Cobalt." 



Now, we must try another substance with, or in, our little chemist 

 P. Acid, and the student need not be alarmed at my extravagance 

 when I teU him it is to bo— gold. A tiny little bit of gold-leaf 

 (which should be quite pure, or he will get colour reactions for 

 copper, &c.) about t^^■ice the size of a pin's head, cut off with the 

 point of a pen-knife, is taken np at the bottom of a red-hot P. Acid 

 bead, and iept there, or it will fly up and alloy the platinum wire, in 

 which event another piece of gold is to bo added, under a powerful 

 OP, when the gold will be rapidly dissolved (no other single 

 known acid is sufliciently powerful to do this), and its oxide, as I 

 have before stated, precipitated in this position, making the bead 

 " muddy." The student is now to take up a small fragment of 

 P. Acid at bottom of the hot bead, and hold it steadily in a good 

 PP, just over half-an-inch from the tip of tho blue. When the 

 proper amount of oxidation has been applied to the bead in this 

 position, which occupies a time, varying with the blower's capa- 

 bilities and the perfectness or otherwise of the pyrocone, the auri- 

 ferous bead will be observed to be a brilliant topaz-yellow when 

 very hot ; then, in cooling, to become green ; then greenish-blue ; 

 and lastly, when nearly quite cold, a beautiful blue-violet colour, 

 called, when otherwise obtained, " the purple of Cassius." 



Colonel Ross begs to inform Major James Cummings (Quciy, 

 page 347) and other intending pyrologists, that he wiU be happy to 

 reply to any private queries on the subject, briefly but concisely 

 put, if sent to him with an enclosed stamped envelope to the 

 following address : — Acton House, Acton, London, W. 



THE BRAIN AND SKULL. 



SOME correspondence has taken place in Knowiedge relating to 

 the human brain and its outer envelope, the skull. It has, 

 therefore, seemed to me that a few notes upon facts well known to 

 anthropologists and craniologists would probably be acceptable to 

 readers of Knowledge. 



There exists among numerous barbarous and semi-civilised 

 peoples, scattered over the world, a very curious custom, perhaps 

 it may rather be called fashion, of deforming the skull in infancy. 

 This custom has existed from the most remote period, so that in 

 some localities it is very difiicult to obtain a sknll, the measurements 

 of which can be relied upon as distinctive of race, from the ancient 

 graves. The ancient Pemvi.ans were particularly addicted to 

 the deformation of the sknll, and the practice still exists among 

 the American Indians ; but the most curious of all these arti- 

 ficially-deformed skulls are those brought from the island of 

 Mallicolo, in the new Hebrides group, a tracing of one of which I 



*All:ali (Arabic, Al-kali), the reverse of acid ; alkalies turn red, 

 moistened litmus-papers blue ; acids turn blue htmns-papers red. 

 Two of the three alkaline metals, potassium and sodium, were dis- 

 covered by a Comishman (Davy) in London in 1805 by means of 

 the " Voltaic pile." Alkalimeter — alkali and meter (Greek) — a 

 measure. 



