VOLTAIC ELECTRICITY. 



VOLUMETRIC ANALYSIS. 



the earth, that the magnitude, figure, order, and beauty of our planet 

 are perpetually miiinfoin**i* 



(The reader may consult Daubeny On Vulramatt ; Poulett Scrope'i 

 Coindtratiuiuo* t'o<cmoe,aod Otology and Foleswoei <>/ Central Pi-ant* ; 

 Lyall, frimctfkt and Jia*al of Otology, and On Jitna, in I'M. Tram., 

 1858; Darwin. Trant. Geol. Sue., QeoL of Vuteauuc ftlandt, Geol. of 

 Sat* America ; De la Beche, ticulogiced Manual; Caldcleugh, in 

 PkilotorJuad Tnuttoetiotu ; Humboldt* Ootm**, TVurett, and frtalite 

 on Rutkt ; Von Buch, On /JU Canary fjamli ; Abich, U., ['tbrr die 

 tfatttr, Ac. dor V*Uiiuekf ItilJumjm in flatten, and Vua fliuitra- 

 titet; 8. TOD Waltenhausen, Allot de l'Kna,uui I'ttcr die \'nU-a*ucke 

 Getteiiu, Ac.; De Beaumont and Dufresnoy, On Auttryne ; Beudant, 

 //Vapory /D'Aubuiuons Geology; Bischof, Mineral Wattrt; Roger*, 

 ' On the Apallachian Chain,' in Report* of Brit. Auoc., 1842 ; Prof. 

 John Phillip*, Treat itc OH Geology ; Mitchell, ' On Earthquakes,' fitil. 

 Tram., 1760 ; Ansted'* Geological Gouip.) 



VOLTAIC ELECTRICITY. [GALVANISM.] 



VOLTAIC TILE. [GALVANIC BATTERY.] 



VOLTAMETER, (ELECrHO-CHEMlBTRY.J 



VOLUME. This word, as meaning a part of a book, ii derived from 

 the old form of a book, a roll (of parchment). But our language take* 

 from the French a tonne of which thu Latin know* nothing; and 

 nltuu mean* bulk , size, or solid content. Thus the volume of a sphere 

 U two-third* of that of it* circumscribed cylinder : the volume of a 

 cone U one-third of that of a cylinder of the same base and altitude, 

 and *o on. 



Under the variou* word*, PRISM, CYLINDF.K, CONE, SPHERE, &c., will 

 be found the mode* of ascertaining their volume*. The mode of 

 finding the volume which is contained under a given surface is a pro- 

 ceo of the integral calculus, which it would be useless to attempt 

 describing within any limits we could afford. 



VOLUMETRIC ANALYSIS. V uluaetrical Analyta. In chemistry, 

 analyvi* comprehend* that series of operation* by which a compound 

 body u resolved into its constituent*. Analysis may be qualitative, 

 and have for its object the mere ascertaining of the number and 

 nature of the constituents, or it may be yuautitatirc, which as 

 well includes the determination of the amount of each ingredient. 

 Quantitative analysis is based upon the great chemical law of 

 definite combining proportions, and may be proceeded with either 

 in a gravimetric*! or in a volumetrica! manner; that is, a body 

 may be isolated and weighed alone in a balance, and its quantity 

 ascertained ; or it may be separated by, and weighed in combination 

 with, another body, whose combining proportion is well known : such 

 is the gravimetric method. The balance, the instrument used for 

 measuring the gravitating force of the compound, may, however, be in 

 part or wholly discarded, and the amount of a constituent of a com- 

 pound be ascertained by noting the volume of a liquid which is 

 required to be added to the compound before a given effect U pro- 

 duced : such is volumetric analysis. Gravimetry is more generally 

 applicable, but requires an exceedingly delicate balance, with perfectly 

 accurate weights, great skill in manipulation, and the expenditure of a 

 considerable amount of time. Volumetric analysis in only applicable 

 to a limited extent ; and the liquids referred to, or standard solu- 

 tions as they are called, sometimes require considerable care in their 

 preparation ; but no elaborate apparatus is necessary. The operation 

 is simple, and easy of execution, and may usually be performed in 

 one-tonth or one-twentieth part of the time necessary for a gravimetrical 

 experiment 



Yolumetrical analysis seems to have first sprung from Richter's 

 observation* on neutral saline solution*, a research which much aided 

 the discovery of the laws of chemical combination. Quantitive estima- 

 tion by the balance, or restricted gravimetrical analysis, existed prior 

 to that time, and was constantly appealed to in determining the truth 

 of these laws, because the balance was already well known, and its 

 indications could be relied on. l/'ntil chemistry began to be 

 applied in the art* and manufactures, there was little or no 

 demand fur expeditious analytical processes ; even the volumetrical 

 prnoeess* of alkalimetry, acidimetry, and chlorimetry, introduced by 

 Desoroucilles, and improved by Gay-Lussac, Dalton, and Faraday, for a 

 long time stood alone ; and not until within the last ten or fifteen 



well as the more commonly occurring proximate principles, can be 

 estimated by volumetric methods. Gases have been almost exclusively 

 analysed volumetrically, but, requiring special and peculiar treatment, 

 their examination is described under GASOMRRIC ANALYSIS, which is 

 generally looked upon as a distinct and separate branch of chemistry. 



An enumeration of all the processes of volumetric analysis would 

 require more space than can be devoted to *uch a subject in thin 

 Cyclopaedia : nor would inch a list be of value for any length of time. 

 The masterly researches of Uunsen and others have already systema- 

 tised and extended the applications of many of these processes ; inn 



This rlew of the (Act of Mr. Orovr'i obwrrtilnn on the chemical pirt of 

 ptatoale sad rolcsnle theory, funned part of * lecture delivered by Mr. llrtvley 

 at UM KuMtll In'tiiutlon, In 1S47, shortly after that obsn-ralion bid been 

 I to the Rorsl Society. 



few years, therefore, it is hoped that an approach to classification may 

 be attained, and that the present inconvenience of having to make, 

 and the difficulty of keeping, so many standard solutions, to a great 

 extent will be got rid of. Moreover, several volumetric methods 

 have already been treated of in this Cyclopaedia [ALKAI.UIKTHY ; 

 ACIDIMETHT; ASSAYINO; CULOBlMirm ; COITKU ; SOAP-TEST; 

 TANMN ; UREA], so that the subject need only be generally treated 

 . : h. ;. . 



The manner in which the processes involved in volumetric analysis 

 are carried out, will be readily seen on referring to any of the articles 

 above mentioned, or in considering a generally applicable process 

 by Bunsen, presently to be described. The only apparatus neces- 

 sary are some pipettes and a few accurately graduated measuring- 

 glasse* of small and large capacity. One of the latter should be capable 

 of delivering fluid both in a free stream and slowly in small drops, A 

 special measuring-tube, or burette, has been contrived for this purpose 

 by Mohr, and U now generally used for the purpose, fiy. 1 is a 

 drawing of the instrument. 



Fig. 1. 



1 Iff. 3. 



Flf. 1. 



It conduit* of a glass tube, a, from three- to five-eighth* of on inch 

 wide, contracted at the lower extremity, b, and graduated. To the 

 contracted portion i* fitted a small piece of vulcanised caoutchouc tube, 

 r. into the other extremity of which a small spout, d, made of narrow 

 glass tube, is inserted. A wire clamp, e, effectually prevents any tluid 

 from passing out of the burette, unless the knobs, , i, are pressed by 

 the finger and thumb of the operator, when the liquid either flows or 

 drop* a* may be wished. The accurate reading off of the height of 

 the solution in the burette i* a matter of great importance ; Erdman 

 recommends, for this purpose, the use of a float, Jig. 2. It is a hollow 

 glass bulb, and is used ** indicated in jig. 8. which represents the upper 

 part of the burette. It must move freely within the burette, and its 

 specific gravity be so adjusted, by enclosing In it a small quantity of 

 mercury, that the upper edge of the liquid in the burette may rut it 

 uniformly on all sides at a line, a, marked round the central portion of 

 it. In order also that the line on the float may be parallel with the 

 graduation on the burette, and that no undue friction may exist be- 

 tween the two glass surfaces, the axis of the float must coincide with 

 that of the tube. In oases where the text, li.|iu.l contains Anything 

 that may act upon the caoutchouc, the end (l>, .'</. 1 ) of the tube may 

 be more finely drawn out and fluid expelled by gradually compressing 

 an india-rubber ball attached to the upper extremity of the burette. 

 Burettes may be specially graduated for a particular clan of operations, 

 as seen under ALKALIMETRY, and ACIDIMKTRY ; the degrees may indi- 

 cate measure* of ten grains each, as described under SOAP-TEST ; or, as 

 now usually adopted in chemical laboratories, the division may be into 

 cubic centimetres. 



By cUanifying the reactions by which reducing or oxidising volu- 

 metric determinations are effected, Bunsen has succeeded in preparing 

 three test-solutions, by which any of the following substances can be 

 quantitatively estimated : mixtures and compounds of iodine, chlorine, 

 bromine, chlorite*, hypochlorites, sulphide of hydrogen, sulphites 



