232 



NA TURE 



{Jan. 8, ii 



19. Prepare nitrogen from ammonium nitrite (i.e. a mixture 

 of potassium nitrite and ammonium chloride). 



20. Explain how, in the above experiments, the gradual de- 

 oxidation of nitric acid yields the several oxides of nitrogen, and 

 lastly, nitrogen itself. 



XII.— Sulphur 



1. Exhibit the different forms of sulphur: flour of sulphur, 

 brimstone or stick sulphur, and crystallised native sulphur. 



2. Dissolve sulphur in bisulphide of carbon, and obtain 

 crystals by spontaneous evaporation. Indicate the identity of 

 this form with the naturally occurring crystals, and its difference 

 from that obtained by fusing sulphur and allowing the mass to 

 cool. 



3. Explain what is meant by allotropic modification, and point 

 out how the one form of crystal passes into the other. 



4. Show the effect of heat upon sulphur melted in a flask. 

 Contrast the brittle mass derived from cooling the sulphur after 

 heating slightly above its melting-point by pouring into cold 

 water, with the plastic mass obtained when cooled in the same 

 way from a high temperature. Point out the changes which 

 occur as the temperature rises, and exhibit the red vapour of 

 sulphur. 



5. Show combustion in sulphur vapour. Insert a coil of 

 copper wire into the sulphur vapour, and show that combination 

 occurs. 



6. Distil sulphur in a small retort. 



7. Pass hydrogen through boiling sulphur, and demonstrate 

 the formation of hydrogen sulphide by its blackening action on 

 lead paper. 



8. Exhibit ferrous sulphide and galena (lead sulphide). Pre- 

 pare hydrogen sulphide (sulphuretted hydrogen) from the former 

 by the action of dilute sulphuric acid. Collect by displacement 

 and prepare a solution of the gas in water. 



9. Show the combustible nature of hydrogen sulphide by 

 burning a jar of the gas, and point out the deposition of sulphur 

 due to incomplete combustion. Demonstrate and explain the 

 decomposition of hydrogen sulphide by chlorine, and show the 

 deposition of sulphur when its solution is allowed to stand 

 exposed to the air and light. 



10. Demonstrate the value of hydrogen sulphide as a means 

 of separating the metals into groups, by adding the solution or 

 passing the gas into solutions of the various metals, as, for 

 example, arsenious acid, copper sulphate, lead nitrate, anti- 

 mony chloride, zinc sulphate, ferrous sulphate, and magnesium 

 sulphate. 



Write down the equations in each case. 



11. Prepare sulphur dioxide by heating copper with sulphuric 

 acid and collect the gas. 



12. Illustrate the condensation of a gas into a liquid by passing 

 sulphur dioxide into a glass tube surrounded by a freezing mix- 

 ture of ice and salt. 



13. Pass the gas into water and demonstrate the acid properties 

 of the solution. 



14. Prepare sulphur trioxide from fuming Nordhausen sul- 

 phuric acid. Add it to water and compare its behaviour with 

 that of the dioxide under similar circumstances. 



15. Describe the formation in the above experiment of sul- 

 phuric acid, explain the properties of oil of vitriol, demonstrating 

 its affinity for water as exhibited by the great heat evolved when 

 the two liquids are mixed. 



16. Explain the barium chloride test for sulphuric acid. 



17. Add barium chloride to a solution of sulphurous acid, and 

 then nitric acid. 



18. Explain that in consequence of the readiness with which 

 sulphurous acid takes up oxygen it acts as a bleaching agent and 

 as a powerful reducing agent. 



XIII.— Carbon 



1. Show the presence of carbon (charcoal) in wood by car- 

 bonising a splinter of wood in a test-tube ; and in white sugar 

 by pouring strong sulphuric acid on to a syrupy solution. 



2. Describe the properties and modes of occurrence of the 

 three allotropic modifications of carbon : (a) the amorphous form 

 (lamp-black and charcoal), and the two crystalline forms, [b) 

 graphite, and (<r) diamond. Describe the octahedral forms of 

 the crystal of diamond and show glass or wood models. 



3. Explain that the same weight of each of these substances 

 when burnt gives the same weight of the same product (carbon 

 dioxide). 



4. Calculate the weight of carbon dioxide obtained from a 

 given weight of any one of these forms. 



5. Prepare carbon dioxide by treating chalk or carbonate of 

 soda (washing soda) with an acid. Prove that the gas thus 

 obtained really obtains carbon by heating a pellet of potassium 

 in the dry gas contained in a small flask. 



6. Demonstrate the high specific gravity of carbon dioxide by 

 ]iouring it from one vessel to another, and showing that it 

 extinguishes a taper. 



7. Pass carbon dioxide over red-hot carbon in an iron tube, 

 and show that it loses a part of its oxygen and is converted into 

 carbon monoxide, a combustible gas, which, on c unbustion, 

 again yields carbon dioxide. Collect the carbon monoxide over 

 water containing caustic soda, and show that the gas does not 

 render lime-water turbid. Then burn it, and show that the 

 residual gas does possess this power. 



8. Pass carbon mo loxide over red-hot coppsr oxide to show 

 the formation of carbon dioxide, and explain the use of carbon 

 monoxide as a reducing agent in metallurgical operations. 



9. Explain the changes which take place in ai ordinary coal 

 fire. Mention the poisonous nature of the carbon monoxide, 

 and state that it is formed in cases of incomplete combustion from 

 insufficient supply of oxygen. 



10. Mention heat of combustion of carbon, and of carbon 

 monoxide, and explain the value of the latter as a fuel. 



11. Explain the reaction which takes place when carbon 

 dioxide is passed into caustic soda and into lime-water, and 

 explain the formation of a soluble carbonate in the first, and an 

 insoluble carbonate in the second case. 



CHARACTERISTICS OF THE NORTH 

 AMERICAN FLORAE 

 \A7HEN the British Association, with much painstaking, 

 honours and gratifies the cultivators of science on this side 

 of the ocean by meeting on American soil, it is but seemly that a 

 Corresponding Member for the third of a century should 

 endeavour to manifest his interest in the occasion and to render 

 some service, if he can, to his fellow-naturalists in Section D. 

 I would attempt to do so by pointing out, in a general way, 

 some of the characteristic features of the vegetation of the 

 country which they have come to visit, — a country of "mag- 

 nificent distances," but of which some vistas may be had by 

 those who can use the facilities which are offered for enjoying 

 them. Even to those who cannot command the time for distant 

 excursions, and to some who may know little or nothing of 

 botany, the sketch which I offer may not be altogether uninter- 

 esting. But I naturally address myself to the botanists of the 

 Association, to those who, having crossed the wide Atlantic, are 

 now invited to proceed westward over an almost equal breadth 

 of land ; some, indeed, have already journeyed to the Pacific 

 coast, and have returned ; and not a few, it is hoped, may accept 

 the invitation to Philadelphia, where a warm welcome awaits 

 them — warmth of hospitality, rather than of summer temperatu r e, 

 let us hope ; but Philadelphia is proverbial for both There 

 opportunities may be afforded for a passing acquaintance with 

 the botany of the Atlantic border of the United States, in 

 company with the botanists of the American Association, who 

 are expected to muster in full force. 



What may be asked of me, then, is to portray certain outlines 

 of the vegetation of the United States and the Canadian 

 Dominion, as contrasted with that of Europe ; perhaps also to 

 touch upon the causes or anterior conditions to which much of 

 the actual differences between the two floras may be ascribed. 

 For indeed, however interesting or curious the facts of the case 

 may be in themselves, they become far more instructive when 

 we attain to some clear conception of the dependent relation of 

 the present vegetation to a preceding state of things, out of 

 which it has come. 



As to the Atlantic border on which we stand, probably the 

 first impression made upon the botanist or other observer coming 

 from Great Britain to New England or Canadian shores, will be 

 the similarity of what he here finds with what he left behind. 

 Among the trees the White Birch and the Chestnut will be 

 identified, if not as exactly the same, yet with only slight differ- 

 ences — differences which may be said to he no more essential or 

 profound than those in accent and intonation between the British 



1 An Address to the Botanists of the British Association for the Advance- 

 ment of Science ; read at Montreal to the Biological Section, August 29, 

 1884, by Prof. Asa Gray. 



