SODA.— Blacic-ash. Revolving Ball-furnace.
811
made daily in any large works. It is usual in mostworks to test the balls in some way or other, never-theless—say a sample from each man’s work daily.In some eases these samples are tested for theiralkalimetrical percentage, for sulphides, and sul-phates. This involves a great deal of labour, andgives after all only very uncertain indications,owing to the difficulty of obtaining a really repre-sentative sample. A much simpler mode of testingcan, however, be resorted to. Whilst the eyereadily detects any excess in sulphides, it is moredifficult to detect whether any sulphate has beenleft undecomposed. It is therefore useful to weigh10 grams, of the sample into a bottle marked for 203c.c. (of which 3 c.c. correspond to the volume of theinsoluble residue), and to shake it up for half anhour with lukewarm water, which can be done withmany samples at a time. The solutions are allowedto subside, and 10 c.c. of the clear liquid are takenout of each, supersaturated with pure hydrochloricacid, a little barium chloride added, and the wholediluted to 20 c.c. If the liquid then appears quite
clear the ball will be pronounced “ good; ” if it beslightly opalescent, it is only “ indifferent; ” and ifthere be a copious precipitate, it is “bad.” Thisrough test serves as a supplementary aid to theocular inspection of the balls.
All the above descriptions refer to the ordinaryEnglish hand-worked ball-furnace, which is sub-stantially the same on the Tyne, in Lancashire , inScotland , and in the few other localities in Englandwhere alkali works exist. The hand-worked furnacehas also lately been introduced into Germany , whereit is now more common than the “ French furnace.”The latter exists in many French alkali works. Itsprincipal difference from the English furnace is itsmuch larger size. It appears that in France thesize of ball furnaces has been more and more en-larged. Payen (“Precis de Chimie Industrielle”)gives the following table showing this gradual in-crease in size, at the same time the weight andnumber of batches, the total work, and the alkali-metrical titre (1 m. = 3'28 feet; 1 kil. — 2-2 lbs.avoirdupois).
Original furnace of Leblanc and Diz6..
Payen’s furnace,.
Darcet’s furnace,.... .
Clement’s furnace,.
u furnace,.
Length ofthe bed.
Width ofthe bed.
Surface ofthe bed.
Charge.
Number ofbatches in24 hours. .
Weightworked in24 hours.
Alkalimetrical
titre.
For 1 metreSuperficial.
Total.
M.
2-00
3-00
3-25
6-00
9-00
M.
1- 40
2- 002-662-003*00
M.
2-80
5-00
7-00
11-00
24-00
Kilos.
130
125
65
136
136
Kilos.
364
725
455
1496
3264
5
6
12
6
6
Kilos.
1820
4340*
5244*
89761
195844
26 to 30
32 to 35
33 to 36
35 to 40
* Sic; the calculation gives 4350 and 5460.
In connection with these figures it will be usefulto remember that the English ball charge of say3 cwts. sulphate of soda, 3^ cwts. of limestone, andcwt. of coals is equal to 393 kilos. That is littlemore than the charge in the smallest French furnace;but the large number of twenty-seven chargesrepresents a total weight of 10,611 kilos., or morethan Clement’s first furnace. The French furnaceshave only a working bed, no “ back-bed ” or “ shelf ”;and they have far more working doors than theEnglish ones—three or four in the side, one in theend (the “ snore holes ” running at each side of it),sometimes even two at the opposite side of thefurnace.
Payen states as the average size of the charges:;—935 kilos, sulphate of soda, 986 of carbonate of lime,480 small coals, and 145 mother salts (residual fromthe refining process). Of such charges six aremade in twenty-four hours, representing a total of5610 kilos, sulphate of soda (about equal to 5 tons10 cwts., or not quite 37 English balls), with anexpenditure of 2800 kilos, coals = 2 tons 15 cwts.The work is done by six furnacemen and sixassistants, in three shifts, relieving each other everyeight hours. The average time iu minutes for eachstage of the operation is as follows:—30 to chargeand spread the batch; 30, 35, and 20 for the 1st,2nd, and 3rd working through; 20 for the lastworking and drawing; 105 for the intervals of restbetween the workings — altogether 240 minutes.
Each batch gives 1525 black-ash (this seems ex-tremely short weight), and shows 38° by the alkali-meter. The raw materials are generally groundaltogether, and the balls, being much denser thanEnglish ones, are also crushed to small pieces.
It does not appear that the large French furnacehas any advantage over the small English furnace.It is very difficult, indeed, to heat the large bed ofthe French furnace quite equally, and to work themass in the same into a completely homogeneousbatch; there seems also to be great danger both of“ burning” the ball, at least' partly, and of causinga loss of insoluble soda. On the Continent thesupervision of the operation is generally very strict,both by the foremen and the chemists, and thedefect of the process may be partly counterbalancedby greater care; and there seems to be besides theless reason for English alkali-makers adopting theFrench furnace, inasmuch as it undoubtedly requiresmuch more manual labour than the English one. Theconsumption of coal (the figure given by Payencan hardly be relied upon as decisive) can hardly beless in the French than in the English process. Itshould be stated that the English form of ball-furnace is now found in many French alkali works.
Revolving Ball-furnace .—The introduction of thisapparatus into alkali works marks an important epoch.The furnace was the invention of Elliott and Rus-sell, who patented it in 1853. Owing partly to theirincomplete mechanical arrangements, and partly to