No. 7.
VOl. XXTII.
THE JOURNAL OF THE
AMERICAN CHEMICAL SOCIETY A REVISION OF THE ATOMIC WEIGHT OF BERYLLIUM. B Y CHARLES
LATRROPP X R S O S S
Received May re, 1904
THE first determinations of the equivalent of beryllium were made by Berzelius in 1815,~ and consisted of a single analysis each of an undoubtedly impure hydrous sulphate and chloride, both of which were probably also basic in character. The results are, therefore, of no interest in a discussion of the atomic weight of this element. In 1842 Awdejew2 carried out an extended investigation on the sulphates of beryllium and was the first to recognize the neutrality of the hydrous sulphate which Berzelius had considered an acid salt. H e also prepared the sublimed chloride by the action of chlorine upon a heated mixture of beryllium oxide and sugar charcoal, and made three analyses of the product which did not show close agreement. They gave an atomic weight approximating 9.8, the high results being unquestionably due to the action of water on the sublimed chloride, as Awdejew 1 SchweiggerJournal, 13, 296. a A n n . der Phys. Pogg , 56, 106 ; Clarke's "Constants of Nature," p. 132.
722
CHAKLES L A T H R O P PARSOXS.
dried his gas by simp!! passing it oaer ca1c;um chlLriiie. Hls ,lurk on the sulph*ite was of much greater valLl.!e. Fcur res:i;:s are given varying froti1 9.18 to 9.49,The ratio 0: ErO to BaSO, IT as determined by precipitating the sulphuric acid v-ith barium chloride, ren;oving the excess of barium and then precipitating the beryllium as hydroxide by ammonia. Apparently 111 attempt was made to weigh the sulphate itself. \\'eereii,l in 1854.!iulilishetl fotir cltterminations oltained from the hj0rnus su;phate by a method quite similar to that used by Aii-rlTjev:, except that he precipitated his beryl!ium hydroxide 6). amrnoi!ium sulphide instead of ammonia, findiiig it to be somewhat scluble in the latter. His results varied from 9.18 to 9.42. The following year Debray? published hi? investigation on beryllium and its compounds, and estimated the equivalent by means of the double oxalate of ammonium and beryllium. H e determined the oxide by calcination after conversion into the nitrate and also estimated the carbon in separate samples by an organic combustion. His three results are far from agreeing closely. but the ratio between the two means of Be@: 4CO, gave Be = 9.34. In 1869 Klatzo? obtained results varying from 9.13 to 9.40 by means of five analyses upon the hydious sulphate, using the same method as Awdejew. Silson and Pettersen4 were the next to take up the subject. in 1880. They had, for several years, been engaged upon investigations of the rare earths and had actively taken part in the controversy upon the equivalency of beryllium, which lasted so man; !-ears. In fact, they were the first chemists to definitely settle the matter by a determination of the vapor-density of beryllium chloride and, quite contrary to their previously held opinion, to establish its bivalency. In this atomic weight work they first attempted to use the sublimed chloride, but abandoned the trial upon finding calcium in their product and their glass tube apparently attacked. They then resorted to the crystallized sulphate as all previous investigators, except Debray. had done, but used an entirely different method, weighing the sulphate A n n der P h y Pogg 91, 124 Ani1 r h i m p h j s , [3] 4 4 , 37 Clarke's ' C o n i t a n t - of iiatnre ? / pyakt Chem 106, 23j Bev d chem Ges 13 14j. 1 2
17 I ?
723
ATOMIC WEIGHT OF B E R Y L L I I X .
itself after pulverizing the crystals and pressing between filterpaper, then igniting in platinum and weighing the oxide produced. Their sulphate too was probably purer than any previously made, having been produced from the sublimed chloride. Their four results agreed very closely, g.og to 9.114. Kriiss and Morahtl published their well-known investigation in 1891, their results also being obtained upon the hydrous sulphate, which they dried over phosphorus pentoxide before weighing. Their sulphate was derived from three different sources and was very carefully purified. They also used very much larger amounts of the sulphate for each ignition than any other investigator had done, which compelled them, however, to blast their specially constructed platinum crucible for unusually long periods of time. They made fourteen closely agreeing analyses, their results varying between 9.02 and 9.088. All results upon the atomic weight of beryllium obtained up to the preseEt time are, therefore, based upon analysis of the hydrous sulphate BeS0,.4H20, with the single exception of Debray, who used the double oxalate Be( N h , ) 2 (C,O,) 2, and may be summarized as follows: Ratio determined.
..................... B e 0 : BaSO, ........................ B e 0 :BaSO, ......................... B e 0 : BaSO, ...................... B e 0 : 4C02 ............ BeS0,.4H20 : Be0 ............. BeS0,.4H20 : Be0
Awdejew.. Weeren Klatzo Debray.. Nilson and Petterson Kruss and Moraht
Mean 0 = 16.
9.34 9.27 9.28
9.34 9.104 9.05
BA1,ANCE .AXD WEIGHTS.
The balance used in the analyses which follow was a new I Staudinger, which was bought especially for this work. The adjustment was so arranged that a difference in weight of I mg. caused a deflection of twenty divisions on the scale, which could easily be read to 0.2 of a division by means of the microscope attachment. The balance was placed in a second case enclosed on all sides and large enough to permit of convenient manipulation when the front was lifted. This case was attached directly to a brick wall 2 feet thick, with a shallow air space between the case and wall and without any floor connection, so that
No.
1
A n n . Chem. (Liebig). a6a, 58.
723
CHARLES LATHROP PXRSONS.
it \vas not subject to any ordinary jar. i t was situated in an evenly heated room. All weighings tvere made by the method of substitution against a tare consisting of a light thin glass n-eighing-bottle, containing 3 piatinum crucible and cone of the same size and shape as those used in the analysis. This tare was treated in all respects the same as the n-eighing-bottles against wliich it was balanced, and both, 011 removal from the desiccator, were \\-iped with a soft cotton cloth and allowed to stand in the inner balance case. This case !vas kept :is t l n 'IS might be b j mean\ of sulphuric acid. The weights were of brass, platinum-plated and \\-ere compare?: individually and against a standard weight by the Kaiserl. Sormal-Xichungs Kommission. I also compared them against each other and my comparisons agreeing closely with those certified to by the commission, their figures were accepted as correct. All weighings were corrected to a vacuum standard. I
PR€I.IlIIShR\
ISYESTIL\TIOSS
The Preparatzoii of Materiai.-The beryllium compounds used in this investigation viere derived from two sources, the first being beryl from Grafton, S. H.. and the second Kahlbaum's Rerylliumhydrat." Beryl is most readily and quickly attacked by fusion with sodium hydroxide, but no container could be procured which was not also acted upon to such an extent as to render it useless. Sickel crucibles on the market are too small to be of use except for analytical purposes, as the fused mass foams badly. The method of Lebeau,l n-110 proposes the high heat of a n electric furnace to volatilize a portion of the silica of the beryl and render the residue easily decomposable by acids, has distinct advantages to those possessed of the necessary facilities. Beryl itself is not affected by any acid, even hydrofluoric, and this fact renders a separation from orthoclase and quartz, which most of the large S e w Hampshire beryls contain, an easy matter. After a careful study of the many other methods for the decomposition of beryl the following procedure was adopted as the most convenient in my laborator>-. The powdered beryl was fused in a Battersea crucible TI ith a mixture of sodium and potassium carbonates and the fused mass turned out to cool on a ' co*iPi R e n d ,
121,h i ,
ATOMIC WEIGHT OF BERYLLIUM.
725
smooth iron plate. The melt was pulverized and washed with water, which removed soluble sodium and potassium salts, notable amounts of silica and some beryllium, but the loss was more than compensated for by the greater ease of the subsequent operations. The moist residue was just barely covered with water and concentrated sulphuric acid added in excess, by which procedure it became at once a dense jelly-like mass, which was easily broken up, dried and heated on a sand-bath to render silica insoluble. The fine, nearly white and dry powder so produced was washed with hot water, potassium sulphate added to the solution and the major part of the aluminum crystallized out as alum. The mother-liquor was oxidized with potassium chlorate and sodium carbonate carefully added in small portions at a time with intermediate boiling until the filtered solution was colorless. IIost of the remaining iron and aluminum are thus precipitated before the beryllium, as Hart' has pointed out, and the selective action is undoubtedly due to the power which beryllium sulphate has of dissolving considerable amounts of its own carbonate. T o the filtered solution sodium carbonate was added with care to avoid any great excess, as the precipitated basic beryllium carbonate is notably soluble in sodium carbonate solution, and the precipitate washed to remove sodium salts. I t was then dissolved in excess o i sulphuric acid and the B e S 0 4 . 4 H , 0 crystallized out on evaporation. After a second crystallization from pure water the sulphate was again dissolved, precipitated by ammonia, filtered and washed, without any attempt, however, to free the gelatinous hydroxide entirely from sulphates. T h e removal of the main part of the ammonium sulphate is advisable, however, as the reverse reaction. Be(Be(OH),),CO,
+ 4(KH4)2S0,= 4BeS04 + SNH, + 7H,O + CO,,
takes place to a greater or less extent on continued boiling, after precipitating the basic carbonate from ammonium carbonate solution, and is, of course, proportional to the amount of sulphate present. The reaction may be easily complete if excess of sulphuric acid is present before neutralization. The beryllium hydroxide was transferred to a large bottle covered with an excess of dilute ammonia and carbon dioxide passed through the 1 This
Journal, 17,604.
726
CHARLES LATHROP PARSONS
liquid. \l.hen iiearl;; saturated, more ammoiiia \vas added, the carbon dioxide shut off and the bottle allowed to stand i n a warm place with occasioiial shaking. The liquid was filtered from some undissolved aluminum hydroxide and \\-as treated \\-ith excess of ammonium sulphicle a s recommended by Scheerer' a i d Icriiss a i d lloraht.2 ;i small ainomt o i a black precipitate was invariably thrown i!o\\-n at this stage. - l i t e r standing ior severa! days. the sclution was filtered, with special care that the Mack prrcipitate was at all times in contact with liquici containing aniixcniuni sulphide. It was then boiled ivith coilstant stirring mitil ammonia tvas evolved and precipitation was complete. 1-igorons s i r r i n g of some form is absolutely necessarJ- a s the granular precipitate settles quickly and ca:ises violent biimping which I have never been able to prevent bv any other method. Thc hasic carbonate thron-n down varies continually iii composition as precipitaticn progresses but the final product has the approsximate formula Be ( E e ( OH),),C03.2H,0 when dried over sulphuric acid. It is slightly soluble in water, so precipitation is never quite ccmplete. At 1o(3' it loses about 1.50 per cent. of 11-ater and contains about 11 per cent. of Reo. L,ike all the basic compoL1nds ~f beryllium which h a ~ ecome under my observation except those of the acetate group to he tlescrihetl later. its C(impoSitiGl1 is ?>Tno means definite. The carhonatc \vas twicr redissolved in I;?ire sulphuric acid and reprecipitatetl froin ammonium carbonate as described aboye except that the treatment with ammonium SUIphicle. although each time repeated, failed to separate any iurther b lac 1; su lph id e. I
