810 SODA.— Black-ash Balls.

which the ball presents in the furnace, whether thecarbonate of lime has been introduced as chalk oras limestone ; it takes about equal time and labourto make a good ball in either case, but there is adecided difference in heat. The furnace must bekept much hotter for chalk than for limestone. Menwho are used to chalk are apt to “ burn ” balls whenthey have to use limestone, whilst in the oppositecase, those used to limestone make “soft” ballswhen they come to use chalk—both, of course,only till they have accustomed themselves to thenew style of work.

Sometimes an arrangement is used by which thefire-damper goes down whenever the working-dooris raised ; this is to prevent a mechanical carryingaway of sulphate by the draught during charging,but such refinement is only rarely practised.

The importance of working the ball-mixture wellwith the paddle and the rake is well illustrated bysome comparative trials made by Kolb on the largescale with a mixture of 106 sulphate, 101 chalk, and53 coal. The analysis of two balls, one of which(A) was well turned over and worked through,whilst the other (B) was badly worked, showed thefollowing result:—

A.

B.

Sodium carbonate,.

62-20

51-20

Sodium hydrate,.

4-72

7'15

Sodium sulphide,.

1-12

4-58

Sodium sulphate,.

2-06

7'48

Together corresponding to sodium)

72'2

63-3

carbonate,.j

The amount of work which is taken out of afurnace varies according to the time the men work.If they work in two shifts during the twenty-fourhours, it is usual to make only 12 balls in each shift,or 24 in the twenty-four hours; but if (as is nowusual on the Tyne) they work in three shifts ofeight hours each, they get 9 balls per shift, or 27balls in twenty-four hours. A greater number ofballs can be made, but scarcely of the best quality.

The amount of fuel used varies according to thequality of coals. The writer has made prolongedtrials with several descriptions of Durham “manu-facturing small,” and found the average consumptionto vary from 25 to 27 cwts. for each ball-furnace(producing the full work of 27 balls) during 24 hours.

The weight of a well-worked ball should be about4 cwts. 3 qrs., but it varies to some extent round thatfigure.

A practical man can easily tell from the appearanceof a ball whether it is good or bad; whether it has beentoo long or too short a time in the furnace ; whetherit has had enough work or not; whether it is shortof limestone (chalk) or coals, or has too much ofcither. A single glance tells him much more in allthese respects than a chemist could make out by acomplete analysis, which would only refer, moreover,to a small portion of the ball, and take a very longtime indeed. It is hardly possible to convey anidea of what a ball ought to be like by meredescription, but a few words may not be out of place

upon this subject. A ball ought to be of a blackish-brown colour before it is broken; more particularlyshould that brown colour (of a lighter shade) appearas a skin on the surface which has been the upperone in the “ pot.” If a ball is too black, it has eithertoo much coals or, which is more often the case, ithas not been fired long enough. When broken, itshould appear honeycombed like pumice, not dense,and of as uniform a texture throughout as possible;the colour should be slate-grey, showing small bitsof coal in some places, not pinkish. If it appearsdense, and not sufficiently honeycombed, it has notbeen long enough in the furnace, and has not gotbeyond the stage described above where the mass isnearly liquid; it is then called a “ soft ” ball, and suchblack-ash is not only badly decomposed, but difficultto lixiviate, and sure to give a low yield. A whitishcolour, generally seen already on the outside, showsexcess of carbonate of lime; many large pieces ofcoal, excess of the same. A pinkish colour testifiesof slovenly work ; equally so does a rough structure,showing streaks of chalk, of coals, &c., runningalongside one another. Sometimes a ball, on breakingup, is found to be of a brick-red colour; oftener, atleast parts of a ball are of that colour (spotted).These balls have been “burned,” that is, they havebeen too long in the fire, either from sheer neglectof the workman, or because he wanted to make upby greater heat for deficient work in “paddling.”It is usual not to pay the man for such “ red ” balls,as they contain a very large proportion of causticand sulphide of sodium, and yield very inferior ash.If a ball were made according to the descriptiongiven by M. Payen, and in many other books—thatis, if it were only drawn when the jets of flame beginto disappear, instead of raking it when they beginto appear —it would most certainly be a “ red ” one,and would be condemned. It is also a mistake toassume that a ball becomes less soluble the more itis fired; on the contrary, the balls which are mostdifficult to lixiviate are those which have not beenlong enough fired (the “soft” ones). This may beeither sheer neglect of the workman, or it may arisefrom bad draughts or other impediments to thefurnace becoming properly heated. Of course, ifa ball were left in a long time after it was reallyfinished, it might again become less soluble; but itwould be so utterly spoiled in that case, that thedifficulty of dissolving it would be one of itsminor faults. It seems, however, certain that thelonger the ball is left in the fire, the more doesthe sodium pass into the state of compounds abso-lutely insoluble in water, and totally irrecoverableby the manufacturer.

The eye of an experienced foreman or manager isby far the best judge of the quality of black-ash,and really much more reliable than the analysis inthe laboratory, for the simple reason that it can takein the quality of the ball as a whole, while thechemist can only test a small sample ; and it isextremely difficult to obtain a sample represent-ing the real average composition of the black-asheven from a single ball, let alone from the hundreds