NATURE 



97 



THURSDAY, DECEMBER i, 1892. 



CHEMICAL LECTURE EXPERIMENTS. 

 Chemical Lecture Experiments. By G. S. Newth_ 



(Longmans, 1892.) 

 ^'/^N revient toujours," &c. and the very description 

 V_y of a good lecture experiment to one who had for 

 thirty years always enjoyed performing an old one, 

 and was overjoyed in bringing out a new one, is some, 

 thing akin to that of the old war-horse when he scents the 

 battle from afar. And both Mr. Newth's experiments 

 and his descriptions are good ; so I think that not only 

 the novices of the profession but the old hands will read 

 this book — the first with profit with a view to what they 

 will do, and the second with pleasure in recollecting 

 what they have done. I was dining some years ago 

 with the great Dumas (I don't mean either of the novel- 

 ists), and after dinner we sat together on the sofa 

 smoking our cigars, when he said to me, " I have been in 

 many positions — professor, minister of state, and in- 

 vestigator — and I have seen the world from many points 

 of view. If I had to live my life again I would not leave 

 my laboratory. The greatest pleasure in my life has 

 been original work ; the second greatest that of teaching 

 a class who appreciated what I was telling them." We 

 all know that Dumas was a master in the art of experi- 

 mental teaching, and those who have practised this art, 

 even at a great distance from the master, will agree with 

 him that the pleasure of giving a well-illustrated experi- 

 mental lecture on chemistry is not a small one, and even 

 that a man may go on for thirty years and yet not be 

 altogether tired of the job. The reason for this 

 is not far to seek. Our science in its daily 

 progress constantly opens up new paths which 

 yield matter suitable for lecture experiment, and 

 this gives a zest to the discourse unattainable by the 

 teachers of most other subjects. Mr. Newth has collected 

 an ample store, and he has described them clearly. For 

 the collection he has had favourable opportunity ; to 

 begin with he was a distinguished student at Owens, and 

 there he may have picked up a few wrinkles ; then he has 

 for many years been Lecture Demonstrator to Frank- 

 land and Thorpe, and from them the wrinkles he has 

 picked up have certainly been many. But although 

 doubtless some are of his own finding out, I think it 

 would have been well if he had added after the descrip- 

 tion of each experiment the name of the authority with 

 whom it originated. Thus some have been described by 

 the chemists I have named, others owe their existence 

 to Hofmann, Bunsen, and others. These additions are 

 not only due to the authors, but would add to the 

 interest of the book. Mr. Newth should see to this 

 in the next edition. The old booksellers tell us 

 that Faraday's " Manipulations " is a work which 

 no lecturer should be without, and as everything which 

 that prince of experimenters wrote or did is worthy 

 of attention, they speak truly, and yet no modern chemists 

 can be bound by Faraday's experience of sixty years ago. 

 Things are not as they were ; and the methods of work 

 and the illustrations of chemical phenomena which he 

 details belong to a bygone age. And so Mr. Newth 

 NO. 1205, VOL. 47] 



comes forward to give the lecturer of to-day a helping 

 hand. The first thing that strikes one on looking through 

 his pages, is how simple are the experiments — so far as 

 illustrating the chemistry of the non-metals goes, and he 

 goes no further — needed to illustrate a course of lectures. 

 We do not require the expensive and delicate instru- 

 ments of the physicist. With glass and india-rubber, as 

 Liebig said, we chemists perform all our mysteries. Only 

 in a few cases, as, for instance, when we want to hand 

 round wine-glasses filled with liquefied oxygen or air, or 

 when we desire to show our students free fluorine and such 

 like things, does the apparatus become expensive or the 

 experiments troublesome. All the ordinary and many 

 of the extraordinary experiments detailed in the book 

 may be carried out with little cost and without great 

 trouble ; indeed most of them may be made by the 

 veriest tyro provided he stick to the letter of the de- 

 scription and does not attempt to vary the proceedings, as 

 one I knew did, who thought that as sulphuric acid is a 

 more powerful desiccating agent than lime, he would dry 

 his ammonia by the former substance instead of by the 

 latter material. No account of any experiment, the 

 author tells us, has been introduced upon the authority 

 solely of any verbal or printed description, but every 

 experiment has been the subject of his personal investi- 

 gation and the illustrations are taken from his original 

 drawings, so that we may be sure that every experiment 

 will "go" if properly managed and fairly dealt with. 

 Many of the experiments are, of course, old stagers, but 

 none the less useful, whilst others are new to me and 

 probably to most people. To mention many either old 

 or new this is not the place, but one of them, which has 

 struck me as interesting is an easy method of showing 

 the freezing of water by its own evaporation first with a 

 common air-pump, and second with no air-pump at all. 

 I always used a Carre's machine, by which a quart of 

 water could be frozen, but Mr. Newth gives an excellent 

 description of how a beautiful icicle twenty to thirty 

 centimetres long can be obtained both with and without 

 an air-pump. The secret of how to do this can best 

 be learnt by reading pages 57 to 59 of the book. 

 " How to float soap bubbles upon carbon dioxide " 

 has often proved a difficult question to answer experi- 

 mentally, because if you managed, after a score of trials, 

 to free your bubble from the pipe on which you blew it, 

 the bubble usually bursts the moment it touches your 

 heavy gas. Mr. Newth lets us into the secret. You must 

 remove every trace of hydrochloric acid,which is carried 

 over with the gas, by washing, the presence of this acid 

 being fatal to the life of a soap bubble. Under chlorine 

 (p. 88) a description is given of the mode of sealing up 

 bulbs filled with chlorine and hydrogen. This was 

 first done in the early sixties by my old helper 

 and friend Mr. Joseph Heywood, of Owens, to whom 

 both students and lecturers owe many an ingeni- 

 ous and striking experimental illustration. As Mr. Newth 

 remarks, there are many obvious reasons why the old 

 plan of filling a soda-water bottle with a mixture of equal 

 volumes of the gases and then throwing it out of the lec- 

 ture-room window into the street, if the sun happened to 

 shine, is " unsuitable for a lecture experiment," and Hey- 

 wood's bulbs answer the purpose better in all respects. 

 The author does not tell us— as he ought to have done — 



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