in grammes of weight of the U-'tube, B gives the number of grains of sulphuretted hydrogen in 100 cubic feet, and C the percentage : A. .lOrjCi
No. 4... . . . . .
.1.100 .1110 .1 lU5
u. 344.91 339.52 342 3 9 341.00
c.
0.51 per ccnt. (1.52 " " 0.52 it I(
,).S?
:i
6t
These I consider as agreeing very closely. A few days after I begali the experiments upon the finished gas and was surprised to find that the 1.f-tIl~Jcgained more in weight than it did when using the unpurified, soiiietimes showing as much as 100 grains more in 100 cubic feet, wliile the Referee's apparatus, as usctl by D r . Love atid also by myself, did iiot give over 10 grains of total sulpliur. After a few attempts I found the sull'hate of coppei. assumed a peculiar tint different from what I liad seeii while working on the unpurified gas, and, tliinking that the sulyhuric acid liberated miglit be iri some way actiiig upon sonie of the hydrocarbons, I took some of the sulphate ( J u t of the tribe and treated it with absolritc alcohol atid ;tlso with clther, : t i i d obtained a peculiar oily substance, apparciitly a mixture of liydrocarboris, l.)ot hxve not as yet been able to obtain a sufticieiit quantity of it to make any experiments upoii it, but hope to be ablv to do so before long. This was sufticieiit, to prove to rnc what caused the increase in weight of the V-tube and slio\ved that it was not, due to sulpliuretted liydvogc~n. I have not yet liad an opportunity to try this method on uripuririves fied coal gas, but accoding t o Mr. Wright's statemetits it b' r e r y satisfactory results.
ON THE FRACTIOSAL DE-HYDRATION OF AXMONIUM ALUM, AND THE ATONICITY O F ALUMINUM BY J. W. MALLET In the course of experiments preparatory to my investigation of the atomic weight of aluminum,* I examined the behavior of crystallized ammoriium-aluminum alum when dried under various conditions, among others when placed over sulphuric acid in a desiccator. _____ __.* Piiilosophical 'Pransactions, 1880, Part 111.
ON THE FRACTIONAL DE-HYDRATION OF ALUM, ETC.
181:
The question of the extent to which water of crystallization is removable, under well-defined conditions, from the alums, bears upon the adoption of the formula
M’31”’ (SO,), 12 H,O Or
& M”’, I’ (SO,), 24 H,O as correctly representing one of these salts. This question hsa been discussed by Lupton and Watts,t on the basis of the experiments of Hertwig ;$ Lupton 5 and Heintz,\/ with the general result that in sundry cases the amounts of water lost, by heating to definite points of temperature, or by evaporation of a solution mixed with excess of sulphuric acid, point to the second of these formuls, from which odd numbers-such as 19, 21 and 23-of molecules of water may be withdrawn, and which therefore cannot be halved and thus reduced to the simpler formula if but B single molecule of the anhydrous salt be supposed to be present in the residue. Having ascertained that ammonium-aluminum alum loses largely of its water of crystallization by exposure to air of ordinary atmospheric temperature and pressure dried by a surface of sulphuric acid, and that the loss, even after it has become very slow, goes on for a very long time, I determined, as a separate question from that with which I was chiefly occupied, to continue the drying under these conditioris until loss of weight should cease, and see what number of molecules of water would be left. The experiment lasted inore than two years, weighings being made at first at intervals of a few hours, then of a day, of two days, of two weeks, and, toward the end, of a month. The temperature of the room, which in winter was warmed continuously b y night as well as day, ranged generally ctbout from 20” to 27” C., but occasionally passed these limits to a considerable extent during long-continued periods of hotter or colder weather out of doors, and such variations of temperature as occurred made themselves perceptible in the more or less rapid loss of weight of the salt experimented on. The alum was in the form of a fine crystalline meal, spread out to the depth of 7 or 8 millimeters over the surface of a platinum capsule about
t Watts’ Dictionary of Chemistry,
3d Suppl., Part I., pp. 65, 66. $ Pogg. Ann., lv., 99. Q Chem. Soc. Jour. (Lond.) [?I, xiii., 201. 11 Pogg. Ann., iv., 331.
ON THE FRACTIONAL DE-HYDRATION O F ALUM, ETC.
7.0279 gram. (7.8812 (' =I0 H,O.) (6 _- 8.2636 '(.. . (8.5593 '' =I1 H,O.) (' - 9.1001 (' (9.3374 '( =I2 H,O.) (6 - 9.6668 (10.1156 I' =13 H,O.) ---10.6028 (10.8937 I' 1 1 4 H,O.) '' ---10.9848 '' '' ----11.5513 " (11.6718 '' =15 H,O.) " -12.2015 '( (12,4499 (' =16 H,O.) " --12.7269 (' (13.2380 " =17 H,O.) -13.4779 (14.0062 '( =18 H,O.) (( -14.0662 '( -14.4133 (' --14.5237 &( [put fresh acid de.iiccator. '( -14.5670 '( '( ---14.5955 -14.6146 (' (' -14.6341 I' ---14.6528 '( -14.6675 '( " ---14.6793 '( -14.6933 '( (' --14.7277 '( -14.7595 " (14.7843 -19 H,O.) '( -14.7847 (' --14,7875 (' '( -14.1875 (' " -14.7858 " (' --14.7955 '(
183
Loss after 42 day 2 hours--
.
'(
((
((
((
'(
((
((
Into
((
((
((
((
((
((
((
Hence it appears that by exposure to dried air under the conditions stated, ammonium alum loses 19 out of 24 molecules of
184
ox
TIIE F R A C T I O Y A L I ) W I I T I ) R A T I O N
~ t A ' L U M , ET(:
w t e r , and tliiis adds 0111' case of definitc partial de-hydration to those cited by Lupton and W a t t s * in fayov of tlic layer formula ---the obscrved residues s t a n d i q as follows (Watts"tal)le, copied ~ ' I X J I ~ Lnptori's I ~ ~ : t p (witli ~ . t h e c a w i i o w re])c~rteil:dtled in brackets) : (SO,),.
(x€I,)lFel(SO,),.
r1,o
IC? AI, (SO,),. 3B10
I
