4-'2 



NATURE 



[January 31, 19 18 



in the French universities, and is by no means un- 

 known in the chemical schools of other countries. 

 The care which is evidently taken in revising- it, 

 and the frequency of its reappearance in the form 

 of new editions, will tend to ensure a continuance 

 of its popularity. 



(4) Prof. Tognoli's little book on " Reagents and 

 Reactions," translated from the Italian by Mr. C. 

 Ainsworth Mitchell, supplies an omission and 

 serves a very useful purpose. As the translator 

 points out, it is a common practice to refer to n 

 reaction by the name of the chemist who first 

 devised it. Indeed, in many cases there is no other 

 convenient method of designating- it. Thus we 

 speak of the Marsh and the Reinsch tests for 

 arsenic, the Nessler test for ammonia, the Bau- 

 douin test for sesame oil — to confine oneself to 

 well-known examples. But some examples which 

 might be quoted are far from well known — many 

 are obsolete and some are wholly forgotten. 

 Physiological chemists, and medical men who 

 dabble in physiolog"ical chemistry, are especially 

 prone to associate their names with minor qualita- 

 tive tests for pathological and similar products, 

 Isuch as albumin, biliary pigments, gastric juice, 

 uiine, et hoc genus omne. Most of these tests find 

 no permanent place in chemical literature, but 

 reference to them may occasionally be made in 

 special papers with no mention of their exact char- 

 acter. On the other hand, there are, of course, 

 others which have been found of great value and 

 are in constant use. 



The author has gathered together a list of the 

 more important reagents commonly employed in 

 such testing, arranging them in alphabetical order 

 and indicating the means of ascertaining their 

 purity. He then gives a more or less detailed 

 account of reactions arranged in the alphabetical 

 order of the names of their discoverers or of those 

 persons with whose name the test is commonly 

 associated — which is not in all cases the same 

 thipg. Condensed as the descriptions of the tests 

 are, the list extends to nearly 140 pages. It is 

 probably sufficiently complete, and we may be 

 reasonably certain that no important chemical reac- 

 tion of the kind has been omitted ; the book there- 

 fore adequately fulfils the intention of the author. 

 In a collective index at the end of the volume the 

 various names are gathered together in connection 

 with the substances for which the tests were de- 

 vised, arranged in alphabetical order. Thus we 

 have thirty-two names in connection with albumin, 

 fifty-two in connection with alkaloids, fifty in 

 connection with dextrose (mostly in urine), 

 and no fewer than 126 in connection with that 

 particular fluid itself. A useful feature in 

 the book is a description of various test-papers 

 for acids and bases ; others for special tests, 

 such as for ozone, nitrites, oxygen, hydrogen 

 peroxide, carbohydrates, oxidising and reducing 

 substances, etc. There is also a short list 

 of test-papers found useful in clinical tests, e.g. 

 the tropaeolin paper of Boas-Liicke for detecting 

 the acids of the gastric juice ; Geissler's potassium 

 mercury iodide and citric acid paper for detecting 

 albumin in urine ; Olliver's indigo-carmine and 

 NO. 2518, VOL. 100] 



sodium carbonate paper for the recognition of dex- 

 trose in urine, etc. There are also tables, by re- 

 cognised authorities, showing the specific gravities 

 of aqueous solutions of ammonia, caustic potash 

 and soda, potassium and sodium carbonates, the 

 common mineral acids," and of methyl and ethyl 

 alcohols, glycerin, and dextrose, with the corre- 

 sponding values, in certain cases on the hydro- 

 meters in common use. 



The book is conveniently arranged, and will be 

 found useful for purposes of reference by analyti- 

 cal and physiological chemists. 



THE WORLD'S WHEAT SUPPLY. 

 The Wheat Problem. By Sir William Crookes. 

 Third edition. With Preface and additional 

 chapter bringing the Statistical Information up 

 to date, and a chapter on Future Wheat Sup- 

 plies, by Sir R. H. Rew. With an Introduction 

 by Lord Rhondda. Pp. xvi-f-ioo. (London: 

 Longmans, Green, and Co., 191 7.) Price 3.V. 6d. 

 net. 

 TT is now nearly twenty years since Sir Wil- 

 -^ Ham Crookes discussed the world's wheat 

 supply in his presidential address to the Bristol 

 meeting of the British Association in i8g8. His 

 address, issued afterwards in book form, has al- 

 ready passed through two editions. This third 

 and revised edition, for the publication of which 

 Lord Rhondda appears to be responsible, could 

 not have appeared at a more opportune moment. 

 No one at the present time can fail to appreciate 

 the gravity of the problem which the author pre- 

 sents. The recent enactment of the Corn Produc- 

 tion Bill shows that even politicians recognise its 

 urgency and have taken steps to secure the pro- 

 duction of a greater area of wheat. 



But it is not to legislative aid that Sir William 

 Ciookes trusts for increased corn production. His 

 hope — to quote his own words — is that " starva- 

 tion may be averted through the laboratory." 

 The argument is briefly as follows : — ■ 



A large and progressively increasing proportion 

 of the world's inhabitants feed upon wheat, and 

 the world's demand for wheat continuously in- 

 ci eases. The possibility of increasing wheat pro- 

 duction by extension of area is shown to be 

 approaching finality. The time must, therefore, 

 arrive in the near future when the world's wheat 

 production will not meet the world's demand, and 

 famine must necessarily follow. This can be 

 averted only by increasing the yield of wheat per 

 acre, which can be most readily achieved by the 

 increased use of nitrogenous manures. 



But the world's requirements for nitrogenous 

 manures for this purpose would rapidly exhaust 

 all possible existing supplies^ — sulphate of am- 

 monia, nitrate of soda, and guano. It is claimed 

 that the fixation of atmospheric nitrogen by a 

 chemical process provides the only practical safe- 

 guard against a rapidly approaching world's wheat 

 shortage. 



It is further stated that the fixation of atmo- 

 spheric nitrogen on a commercial scale is a prac- 

 i ticable proposition, for its development has pro- 



