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The Country Gciitlcinaiis Magazine 



^grtctiltottil iniplemcnts ant) ittiichinc! 



THE PREVENTION OF FORMATION OF SCALE IN BOILERS. 



BESIDES the substances which act chemi- 

 cally, like soda ash, chloride of barium, 

 carbonate of ammonia, extract of oak bark, 

 &c., to prevent the, formation of scale in 

 boilers, there have been from time to time, 

 says the Scientific American^ materials pro- 

 posed which act either by commingling with 

 the mineral particles, thus retaining them in 

 suspension, or by rendering adhesion difficult. 

 Professor Bolley, late professor of applied 

 chemistry at the Polytechnic School at Zurich, 

 Switzerland, -has investigated this subject, and 

 we find in his report much valuable informa- 

 tion. Saw dust from mahogany, as well as 

 from coniferous trees, has been used with 

 success. The former acts also chemically, 

 as well as mechanically, owing to the tannic 

 acid it contains. This acid combines with 

 the lime, forming tannate of lime, which de- 

 posits itself as a slimy body, without adhering 

 to the walls of the boiler. The saw dust from 

 pine and other similar woods possesses only 

 a mechanical action. Both, however, are 

 soon reduced to a slime, and are thus objec- 

 tionable for the reason that they are easily 

 thrown by priming between the valves and 

 the packings of the piston, and interfere seri- 

 ously with their operation. 



Clay free from sand has been proposed by 

 a Frenchman, Isl. Chaix, and has been found 

 to answer well : boilers, in which it was used, 

 were found free from scale two or three months 

 afterwards. Still, its use has been discon- 

 tinued, owing to the fact that the valve sur- 

 faces and the interior of the steam cylinders 

 have been found scratched and covered with 

 dirt. 



Scrap iron acts not on the sides, but merely 

 on the bottom, which is often much worn by 

 its use. 



Among others, starch and sugary sub- 

 stances have been applied. Potatoes have 

 been in use for a long time for the purpose 

 in question. The starch, of which they mainly 

 consist, is soon converted into dextrin or 

 starch gum, whereby the water becomes 

 viscid. Molasses acts in the same manner^ 

 as observed by M. Guinon in Lyons (France), 

 and confirmed by Guimet ; and both these 

 gentlemen state that for a boiler of 1 7 ^ feet 

 length and 8^^ feet diameter, 10 lb. of mo- 

 lasses was amply sufficient to completely pre- 

 vent the formation of scale for two months. 

 Formerly it was necessary to remove the scale 

 every month from this boiler. Guimet uses 

 6 lb. of starch syrup every month in a 

 boiler of 8-horse power, with the best 

 success. Steam is kept up in the boiler in 

 question for fourteen hours a-day. To the 

 same series of substances belong also dye 

 wood extracts, since they yield glucose when 

 acted upon for some time by hot water. This 

 substance produces the same effects as sugary 

 liquids. Bran and succory root, both of 

 which contain starch, belong to this class. 

 Payen recommends to add to the water in a 

 boiler producing 600 lb. of steam daily, per 

 month, 9 lb. mashed potatoes, 3 lb. mo- 

 lasses, I -5 th lb. dye wood extract, or, in- 

 stead of the last named, 3 lb. of bran. As 

 dye wood extracts contain tannic acid, they 

 will also act chemically ; hence the small 

 amount recommended. It may be well sup- 

 posed that all slimy substances, or such that 

 are rendered slimy, continuously prevent the 

 deposit of the mineral because their smallest 

 particles serve as points of agglomeration for 

 the minute crystals, and thus render their ag- 

 gregation and accumulation impossible. But 

 there is one grave objection to the application. 



