April 2"], 1876] 



NATURE 



507 



DITTMAR'S CHEMICAL ANALYSIS 

 A Manual of Qualitative Chemical Analysis. By 

 William Ditlmar, Professor of Chemistry in Ander- 

 son's University, Glasgow. (Edinburgh : Edmon- 

 ston and Douglas, 1876.) 

 ■\ T T" ITH the numerous works on chemical analysis already 

 V V in existence we are justified in asking what special 

 advantages Prof. Dittmar has to offer to chemical students 

 in bringing out another book on the same subject. It wnll 

 be found, in answer to this question, that the present 

 work contrasts favourably with many of our standard 

 books on the subject both as regards completeness, ori- 

 ginality of treatment, and the introduction of a large 

 amount of important matter which has not hitherto found 

 its way into our manuals of analysis. 



In giving our readers a brief sketch of Prof. Dittmar's 

 mode of treatment, we shall point cut what appear to us 

 to be the special features in the new analysis deserving 

 commendation. 



To quote from the " Introduction " : — " The book is 

 intended for the use of students who, after they have 

 mastered the first rudiments of chemistry, enter a labo- 

 ratory to work under the ditection of a teacher, while, at 

 the same time, they continue their study of theoretical 

 chemistry." 



Following the Introduction, we have a series of exer- 

 cises calculated to make the student practically acquainted 

 with most of the operations and processes employed in 

 analysis. Among the readable matter interspersed be- 

 tween the exercises, we notice with satisfaction a clear 

 elucidation of the meaning of the term equivalent — a 

 term which appears to have dropped out of most of the 

 modern text-book;-, leading students to believe (we speak 

 from actual experience) either that the idea is altogether 

 obsolete or is covered in some mysterious way by the 

 word '' atomicity." 



We are of opinion that the meaning of "equivalent," 

 or '" equivalent weight " of an element, should be laid 

 before all students of the science and the relationship of 

 these numbers to the " atomic weights " clearly pointed 

 out. In this same portion of the book will be found also 

 an excellent exposition of the general theory of double 

 decomposition. 



The next division treats of the metals, these being 

 divided into six groups, viz., the copper group, comprising 

 silver, mercury, lead, copper, bismuth, cadmium (and 

 palladium) ; the arsenic group, comprising this metal, 

 antimony, tin (molybdenum, tungsten, gold, platinum, and 

 the platinum metals other than palladium) ; the iron 

 group comprising chromium, aluminium, iron (uranium), 

 cobalt, nickel, manganese, zinc (thallium), &c. ; the 

 barium group comprising this metal, strontium, and 

 calcium ; the magnesium group consisting of this metal 

 and lithium ; and the potassium group comprising sodium, 

 potassium (rubidium and caesium). The method here 

 adopted does not much differ from that in general use, 

 excepting that the groups are considered in the same 

 order as that followed in the systematic course of analysis 

 instead of in the inverse order. After the reactions of 

 each of the metals in the group have been considered, 

 their separation from each other and, from the other 

 groups is entered upon. We are glad to see that in many 



cases the author does not limit himself to one particular 

 method of separation, but gives the most effective methods 

 known, and points out under what particular conditions 

 each process is applicable. The reactions of the rarer 

 metals are given in appendices to the main groups. We 

 observe also that Bunsen's flame reactions are sometimes 

 resorted to, this being, so far as we know, the first work 

 since the last edition of the English translation of 

 Fresenius' *' Qualitative Analysis," in which these valuable 

 film-tests are introduced to the notice of students in this 

 country. This portion of the book concludes with a 

 general scheme to be followed in performing a systematic 

 analytical search for metals. 



The third division of the work treats of the non- 

 metallic elements. In |each case the properties of the 

 free element are first considered, then its reactions and 

 the reactions of its acid compounds, and finally the dis- 

 crimination of the element and its acid compounds in 

 complex mixtures. The order in which the various groups 

 are treated of is as follows : — The halogens, sulphur, 

 selenium, and tellurium, nitrogen, phosphorus, boron, 

 silicon, fluorine, carbon, hydrogen, and oxygen. This 

 list of course gives no idea of the complete manner in 

 which the author has treated the subject. That our 

 readers may form a more just estimate of the contents of 

 the work, we propose to point out a few selected details. 

 Thus the chapter on the hr\logens includes a description 

 of the oxygen acids of tLese elements and the organic 

 halogenides ; under the sulphur group we have, in addi- 

 tion to the reactions of the sulphides, sulphites, and sul- 

 phates, a discussion of the characters of the dithionates, 

 polythionates, and organic sulphur compounds ; under 

 nitrogen we find ammonia, the oxides and acids, and 

 organic nitrogen compounds (ammonium compounds are 

 treated of as an appendix to the potassium group of 

 metals) ; the acids of phosphorus are considered in great 

 detail, and a section devoted to organic phosphorus com- 

 pounds. The chapter on carbon includes the analytical 

 characters of a large number of organic bodies, cs;., 

 cyanogen and its compounds, the fatty acids, the acids of 

 the lactic and oxalic series ; also a section on the ultimate 

 analysis of carbon compounds. Under hydrogen the 

 author treats of water, and under oxygen we find remarks 

 on ozone, hydrogen peroxide, and a verj- complete section 

 on the detection of this element in a combined state. 

 This division concludes with a *' Summary of operations 

 available for the detection of the non-metallic constituents 

 of substance in general, and of the inors^anic acids in a 

 mixture of metallic salts in particular." 



Having mastered the analytical reactions of the metals 

 and non-metals the student is, in the concluding division 

 of the work, introduced to the analysis of substances 

 of unknown composition. The preliminary chemical 

 examination is conducted in the usual manner— some of 

 the substance is first heated fier se, then in a current of 

 air, with " bisulphate rf potash," v-ith soda-lime, a mix- 

 ture of caustic soda, nitre, &c. Then follows an account 

 of the well-known flame and blowpipe leactions and of 

 Bunsen's " film tests." The preliminary examination in 

 the wet way is next undertaken, and this is followed by 

 a section on "methods of disintegration for sone of the 

 more frequently occurring classes of substances." With 

 regard to the exhaustive analysis of complex mixtures, 



I) D 2 



