554 



NATURE 



{April 8, 1880 



43 ••• 474 ••■ Tomkins's standard, 166S; Father Smith's high 

 pitch at old Durham and old St. James's 

 Chapel Royal organs, 1683 and 1708 ; the 

 Jordans, at St. George's, Botolph Lane, 1748 ; 

 English A foot organs. 



45 ... 4S1 ... St. Catherine's, Hamburg, 1543. 



46 ... 484 ... Old smaller organ in Cathedral, Liibeck. 



48 489 ... St. James's (S. Jacobi), Hamburg, original pitch, 

 16S8. 



S. Church Pitch Highest. 



50 ... 494 ... St. James's (S. Jacobi), Hamburg, present pitch, 



1879. 



51 ... 496 ... Rendsburg organ, 1668. 



53 ••• 5°4 ••• Schlick's high pitch, 1511 ; Mersenne's ton dc 



chapelle, 1636. 



54 ... 506 ... Halberstadt organ, 1361. 



9. Church Pitch Extreme and Chamber Filch Highest. 



73 ••• 563 ••■ Mersenne, ton de chambre, 1636. 



74 ... 567 ... Usual church pitch in North Germany in 1610, 



called chamber pitch by Praetorius. Probable 

 pitch of church music of Orlando Gibbons 

 (1583-1625). 



Alexander J. Ellis 



THE A TOMIC WEIGHT OF ANTIMONY ' 

 TN a previous paper on this subject, 2 we gave our reasons 

 -■"• for the opinion, since fully confirmed, that the bromide of 

 antimony is the most suitable compound of this element, as 

 yet known, for determining its atomic weight; and the re-ults 

 of fifteen analyses of five different preparations of the bromide 

 were published, which gave for the atomic weight in question 

 the mean value 120*00 with an extreme variation between 

 119*4 and 1204 for all the fifteen analyses, and between U9'6 

 and 12C3 for the six determinations in which we placed most 

 confidence. The antimonious bromide used in these determina- 

 tions was purified first by fractional distillation, and secondly by 

 crystallization from a solution in sulphide of carbon. In the 

 crystallised product thus obtained, the bromine was determined 

 gravimetricalty as bromide of silver in the usual way. Although 

 it seemed at the time that the results were as accordant as the 

 analytical process would yield under the unfavourable conditions, 

 which the presence of a large amount of tartaric acid in the 

 solution of the bromide of antimony necessarily involved ; yet it 

 was obvious that the agreement was far from that which was 

 desirable in the determination of an atomic weight, and our chief 

 confidence in the accuracy of the mean value — independently of 

 its remarkable agreement with previous results — was based on the 

 fact that the known sources of error tended to balance each 

 other. Hence our conclusions were stated with great caution, 

 and the hope was expressed that after a more thorough inves- 

 tigation of the subject we might be able "to return to the 

 problem with such definite knowledge of the relations involved 

 as will enable us to obtain at once more sharp and decisive 

 results than are now possible." Unfortunately this investigation 

 has been delayed by causes beyond our control. 



In our previous paper we described a simple apparatus which 

 we devised for subliming iodide of antimony ; and in a note to 

 the paper we stated that we were applying the same process to 

 the 1 reparation of the bromide of antimony, and that it promised 

 excellent results. Our expectations in this respect have been 

 fully realised, and the product leaves nothing to be desired either 

 as regards the beauty or the constancy of the preparation. The 

 fine acicular crystals are perfectly colourless, and have a most 

 brilliant silky lustre. With ordinary precautions they can be 

 kept indefinitely without change, and it is easy therefore to 

 determine the weight of the material analysed to the tenth of a 

 milligramme. 



• We have carefully studied the causes of error involved in the 

 analytical process of determining bromine in an aqueous solution 

 of bromide of antimony and tartaric acid by the usual gravi- 

 metric method. These causes we propose to discuss in a future 

 more extended paper. In this preliminary notice we have only 

 space to state that we have satisfied ourselves that the small 

 differences between the results previously obtained arose wholly 



1 Contributions from the Chemical Laboratory of Harvard College. Pre- 

 liminary notice of Additional Experiments. By Josiah P. Cooke, Erving 

 Professor uf Chemistry and, Mineralogy. 



2 Proc . Atner. Acad. Arts and Sciences, vol. xii. page 1. 



from the analytical process, and not from any want of constancy 

 in the material analysed ; and further that these sources of 

 error are to a very great extent under control. Moreover, we 

 have found that the volumetric determination of bromine by 

 silver was not materially affected, if at all, by the same causes. 

 We have thus been led to devise a mode of testing the atomic 

 weight of antimony, which, while it has all the advantages of the 

 gravimetric method previously employed, is free from its sources 

 of error. 



If the atomic weight of antimony were l22"oo, it "would 

 require 1*7900 grammes of pure silver to precipitate the bromine 

 from a solution of 2'0C00 grammes of antimony bromide, while 

 if the 'atomic weight of antimony were i20 - oo it would 

 require l*8ooo grammes of silver. Now it is easy to estimate 

 volnmetrically T A (T of this difference with great certainty. We 

 therefore prepared with great care a button of pure metallic 

 silver, which we annealed and rolled out to a thin ribbon. 

 We then weighed out from two to four grammes of bromide 

 of antimony, prepared by sublimation as described above, and 

 dissolved this salt in an aqueous solution of tartaric acid, which 

 we then transferred to a litre flask and diluted to about 500 

 cubic centimetres. We next very accurately weighed out a 

 quantity of silver slightly less than that which calculation showed 

 was required for complete precipitation. This silver was dis- 

 solved in nitric acid, and the solution having been evaporated 

 to dryness over a water bath, the silver salt was washed into the 

 flask containing the bromide of antimony. As soon as the 

 supernatant liquid had cleared, the small additional amount of 

 a normal silver solution required to produce complete precipita- 

 tion was run in from a burette, and measured with the usual 

 precautions. We used no extraneous indicator, because it was 

 important not to introduce any possibly new disturbing element 

 into the experiment, and in the titration of bromine with silver 

 the normal and familiar phenomena, which mark the close ot 

 the process, furnish a very sharp indication. The details of one 

 of the determinations were as follows : — 



The weight of the bromide of anatomy used amounted to 

 2*5032 grammes. To precipitate the bromine from the solution 

 of this material 2*2404 grammes of silver would be required it 

 Sb = 12200 and 2*2529 if Sb = 120*00. We weighed out, 

 with as much accuracy as if we were adjusting a weight, the 

 smaller of these two quantities of metallic silver, and after 

 dissolving the pure metal in pure nitric acid, evaporating the 

 solution to dryness and redi-solving in water, we added at once 

 the whole of this silver solution to the litre flask containing the 

 solution of bromide of antimony, in the manner described above. 

 It was then found that I2 T \ cubic centimetres of a normal silver 

 solution (one gramme of silver to the litre) were required to 

 complete the precipitation. It will be seen that the weights of 

 thebromile of antimony and silver used could be thus deter- 

 mined with the most absolute precision, and we have the greatest 

 confidence in these values to the -jV of a milligramme. More 

 over, it will be noticed that the volumetric method is only u ed 

 to estimate the difference in the atomic weight which has been 

 in question, and that if the method were only accurate to the ,V 

 of the quantity to be measured it would give as the value of the 

 atomic weight within & of a unit ; while if, as we had reason 

 to believe, the process was accurate within 1 per cent, it 

 would fix the atomic weight within yf^ of a unit. 



By the method just described, the following results were 

 obtained. The letters a and b indicate different preparations. 



Percent, of Br 

 Ag=-io8 Br=8o. 

 66*6643 

 66*6620 

 66*6644 

 66*6696 

 666653 



,. 66*6651 1 200I 



Mean value of fifteen gravimetric de- { 66*666*; 



terminations previously published \ 



Theory Sb. 120 requires 66*6666 



„ Sb. 122 „ 66*2983 



In order still further to control the work, we collected the 

 bromide of silver formed in the last two determinations, washing 

 the precipitate with the precautions which experience had shown 

 to be nece=sary, and determining its weight, first, after drying 

 at 150° C,. and, secondly, after heating to incipient fusion, in 



