CHEMISTRY. 



noxido of manganese, and many other natural 

 (>\i!i-> of manganese, but also that these sub- 

 htiinri > arc i- 1 -nmrkably well adapted for use in 

 all r.ises where ozone would be effective as an 

 agent of disinfection. The following reactions 

 have boon determined by Valmagini : 1. Ozone 

 :ipor, prepared with starch and iodide of 

 potassium, is immediately rendered blue with- 

 out the addition of an acid. 2. A solution of 

 dii'inieally-puro iodide of potassium is imme- 

 diately diTumposed by fragments of the min- 

 eral, and the separated iodine can be detected 

 by starch or bisulphide of carbon, or by vola- 

 tili/ution. 8. Artificially-prepared, chemically- 

 puro binoxide manifests precisely the same re- 

 actions. 4. The powdered mineral strewed 

 upon chemically-pure silver, and moistened, 

 immediately produces a brown stain of oxide 

 of silver, as is shown by its disappearance on 

 ignition. 5. Air becomes ozonized by passing 

 over the mineral, or surfaces coated with its 

 powder. C. Tincture of guaiacum is turned 

 a deep blue by these manganese minerals. 7. 

 Gases resulting from putrefaction are also rap- 

 idly destroyed by them. A number of possi- 

 ble sanitary applications of these minerals are 

 suggested, among them the coating or plaster- 

 ing of sewers, or smoke and gas flues, the treat- 

 ment of waste-water pipes, and use in manu- 

 factories, stables, cellars, etc. 



New Disinfectant. A new disinfecting com- 

 pound, known as the " Universal Disinfect- 

 ing Powder," is highly commended in the 

 chemical journals. It consists of Cooper's 

 salts and sulphate of zinc. It has been ana- 

 lyzed by Prof. Wanklyn, who reports upon it 

 as follows : u This powder contains 70 per cent, 

 of mixed chloride of sodium and chloride of 

 calcium, and about 6 per cent, of anhydrous 

 sulphate of zinc (equal to about 12 per cent, 

 of hydrated sulphate), a little insoluble mat- 

 ter, and 15 per cent, of moisture. 



Spontaneous Combustion of Coal. The 

 British Government commission appointed to 

 inquire into the spontaneous combustion of 

 coal in ships has made its report a document 

 of very considerable practical interest. In this 

 report the development of heat in coal-cargoes 

 is attributed to chemical changes which cer- 

 tain substances undergo through the agency of 

 atmospheric oxygen. 



The best known of these substances are combina- 

 tions of sulphur and iron, known as iron pyrites. 

 The presence of moisture in the air promotes the 

 oxidation of pyrites; it does so apparently by bring- 

 ing the atmospheric oxygen into more intimate con- 

 tact with the surfaces of the oxidizable material. 

 The oxidation of pyrites is accompanied by the de- 

 velopment of heat, which may accumulate to such 

 an extent as to lead to ignition. 



But there is another cause of ignition. Coal varies 

 considerably, not only in chemical composition, but 

 in structure, some varieties being comparatively 

 open and porous, others compact or laminated, very 

 friable and readily broken up. Carbon in a finely- 

 divided or porous condition lias the property of ab- 

 sorbing and condensing within its pores large 

 volumes of certain gases, among which is oxygen. 

 The condensation of a gas by a porous body is at- 



tended by the development of heat. Moreover, tie 

 tendency to oxidation, which carbon und certain 

 KMUpOtudl of carbon i>oc(t. in favored \>\ tl.u 

 condensation of oxygen within their pore*, whmbf 

 the very intimate contact between the curbon and 

 oxygen particle* is promoted. Ik-nee the develop- 

 ment of boat by absorption und the etubtihhineiit 

 of oxidation occur simultaneously. Oxidation in 

 accelerated as heat accumulate* ; chemical ueiioa 

 iiroeeedtt HO energetically that tLe carbon may be 

 heated to igniting point. The breaking up of ttocool 

 before and during shipment by the rough usage to 

 which, for the sake of Bi>ecdy loading, it in often Kub- 

 jected, obviously favors the absorption of oxygen 

 and increases the tendency to beating by this pro- 

 cess. The second process is not, like the lin-t, 

 facilitated by moisture. On the contrary, the wet 

 fills up the pores and diminishes the power of ab- 

 sorbing oxygen. 



In a tropical voyage, coal, confined in the close 

 hold of a ship, will accumulate an amount of heat 

 which no practicable ventilation will suffice to re- 

 move. " Such circulation of air as may be estab- 

 lished, even in the less compact portion of the cargo, 

 is not likely to have any valuable cooling effect, ana 

 the circulation, if there be any, must be very feeble 

 among the more closely-lying masses of small coal; 

 so that heat, if developed in these, will accumulate 

 undisturbed." Indeed, its development would be 

 favored by the fresh supply of oxygen which a 

 gradual replacement of the air surrounding those 

 parts would convey, " so thut a period would be 

 reached sooner or later when the development cf 

 heat would be most seriously promoted by ventila- 

 tion." Thus the commissioners found that the 

 calamities occurred chiefly in tropical voyages. They 

 also ascertained that the percentcge of loss increased 

 with the amount of the cargo. 



The commissioners found it generally recognized 

 in the trade that the breakage of coal was an evil to 

 be guarded against. Their conclusion is that the 

 machines known as "tips" and " spouts" conduce 

 most to the breakage of the coal. In the system of 

 loading by hoist or by crane the fall from the bottom 

 or end of the wagon into the ship's hold is as great 

 as from the mouth of the shoot or spout ; but tho 

 coal, until released from the wagon, is literally un- 

 disturbed, and the fall from the bottom or end of the 

 wiigon, as the case may be, into the spout, together 

 with the concussion of the coal in its passage down 

 the spout, is avoided. Even in this system, Low- 

 ever, the fall of the coal first put onboard is in detp 

 ships very considerable. To obviate the breakage 

 consequent on this fall, anti-breakage boxes weie 

 introduced. The Peninsular and Oriental Company 

 among others use the box or barrow system. It bad 

 been noticed by witnesses examined that the burn- 

 ings of ships often commenced under the main 

 hatch ; but the principal objection of ship-owners 

 to the breaking of coal was that it diminished the 

 value of the cargo. It is now found that the break- 

 age is unprofitable and dangerous. 



The commissioners observe that there is a very 

 common confusion between explosions end sponta- 

 neous ignition. Explosions are never spontaneous. 

 The gas which causes explosions in mines or on 

 ships is marsh-gas light carbureted hydrogen. 

 When mixed with a considerable volume of air, it 

 forms a compound which will explode on contact 

 with flame. If coal, from seams which are charged 

 with marsh-gas, is placed on board ship shortly 

 after beine raised fiom the pit, there is obviously 

 great liability to the formation of an explosive at- 

 mosphere in the hold or bunker*. Dr. Percy and 

 Prof; Abel observe in their paper appended to the 

 report : " Every possible means should in such 

 cases be bad recourse to for facilitating tho escape 

 of gas from coal into the open air. But, as the gas 

 requires a large admixture of air to render it vto- 

 leiitly explosive, it is obvious that any attempt to 



