34 



NATURE 



[March ii, 1920 



There is only one way to learn practical 

 chemistry, and that is to study the work as well 

 as do it. A student should not pass from an 

 ■estimation until he knows definitely the reason for 

 every step in the process, how it can be proved 

 to be complete, and why the operation is done in 

 the way it is rather than in an alternative way. 

 He should make a rule of proving that his pro- 

 duct is what he means it to be, and that it is 

 pure. In short, he should make a thorough study 

 of every piece of work. He may get fewer results, 

 but he will have learned more chemistry, and he 

 will have gained the only true confidence, namely, 

 that founded on knowledge. 



We deprecate, as a rule, general instructions, 

 such as that every precipitate should be ignited 

 two or more times until it ceases to change in 

 weight. Some products need it, some do not. 

 The point for consideration is, What is present 

 that it is desired to get rid of by the ignition, 

 and what conditions are necessary to eliminate it 

 with certainty? Unless the student knows this 

 and concentrates his attention upon it, he is work- 

 ing by mere rule of thumb. As to purity of pro- 

 duct, we have known a conscientious and careful 

 worker to get a good result for one of the minor 

 constituents of an ore, but when it was suggested 

 that he should examine the product that he had 

 weighed, he did so, and found that it did not 

 contain even a trace of the compound of which 

 he thought it consisted. 



(i) The manual by Drs. Gumming and Kay is 

 an excellent text-book for students. It includes 

 a full course of mineral analysis, finishing with 

 instructions for the analysis of several alloys and 

 ores, gas analysis, water analysis, organic 

 analysis, the determination of molecular weights, 

 and various desirable tables. There are many 

 helpful and practical hints, though we think that 

 some parts might profitably be a little expanded 

 on the lines indicated above. The method of 

 igniting ferric hydrate without separation from the 

 filter paper containing it is, of course, not original 

 with the authors, but we think that it will be 

 found generally to lead to a notably short weight, 

 because the reoxidation of the reduction products 

 is very uncertain. 



(2) This "Part" of Messrs. Neville and New- 

 man's course deals only with exercises on "pure 

 organic chemistry." It covers the examination of 

 many classes of organic bodies, finishing with pro- 

 teins and enzyme action. It is a well-arranged 

 course for students of agriculture. Like so many 

 others who refer to the production of acetaldehyde 

 for detection purposes, the authors describe its 

 odour as characteristically fruity. 



(3) The "Chemical Calculation Tables" include 

 NO. 2628, VOL. 105] 



a five-figure table of logarithms with a double 

 thumb index that enables the user to turn imme- 

 diately to any desired page either backwards or 

 forwards. There are extensive tables of factors 

 and weights, giving both the number and the 

 logarithm, and tables referring to gas calculations 

 and molecular weight determinations. It is exactly 

 what one wants to facilitate calculations in the 

 laboratory. . C. J. 



^(otanical Guides. 



(i) Applied Economic Botany: Based upon Actual 

 Agricultural and Gardening Projects. By Dr. 

 M. T. Cook. (Farm Life Text Series.) 

 Pp. xviii-f26i. (Philadelphia and London: 

 J. B. Lippincott Co., 1919.) Price 75. 6d. net. 



(2) Some Familiar Wild Flowers. Photographed 

 by A. E. Sulman. Pp. ii + 65. (Sydney: 

 Angus and Robertson, Ltd., n.d.) Price is. net. 



(3) Australian Wild Flowers. Photographed by 

 A. E. Sulman. Second Series. Pp. ii + 6i. 

 (Sydney : Angus and Robertson, Ltd., n.d.) 

 Price 15. net. 



(4) A Popular Guide to the IVild Flowers of New 

 South IVales. By Florence Sulman. Vol. ii. 

 Pp. xxxi -t- 249+ 71 plates. (Sydney: Angus and 

 Robertson, Ltd., 1914.) Price 65'. net. 



T' 



ng ; from the preface we learn that 

 it is intended as a guide to experimental 

 work in the study of plants, such as should be 

 carried on in any high school, and as a pre- 

 liminary work to the agricultural studies which 

 are now recognised in many high schools. These 

 objects would be served by a good general prac- 

 tical introduction to the study of plant life, and 

 this, we gather, is what Dr. Cook is attempting. 

 Part i., "Plant Life," occupies nearly three- 

 fourths of the volume. Beginning with the seed 

 and seedling, the form of the various plant organs 

 and their uses to the plant are described in suc- 

 cessive chapters, and exercises for practical work 

 are suggested at the close of each chapter. A 

 short chapter on the anatomy of the angiosperm- 

 ous plant follows, then a brief description of the 

 chemical composition and a chapter on plant 

 food and growth, and finally very short chapters 

 on the Gymnosperms, ecological relations, 

 forestry, plant-breeding, weeds, Pteridophytes, 

 Bryophytes, Thallophytes, and Bacteria. 



The remainder of the book, part ii., entitled 

 "Important Families of Economic Plants," is an 

 account of a number of plants of economic value 

 arranged in their families, with a short and often 

 very inadequate description of the characters of 

 each family. The general effect is scrappy. There 



