It is generally considered that water containing carbonate of lime is less injurious for feeding steam boilers than such with sulphate of lime in solution, inasmuch as the latter shows more tendency to form a hard and adhering incrustation. Albeit deposits of this character have been analyzed that present a considerable percentage of carbonate of lime, their number is few in proportion to those in which the greater part of lime is known to exist as a sulphate. The addition of carbonate of soda to selenitic waters, as those of the latter class p,re termed, has at least proved to be an effective means, inasmuch as it causes the formation of a muddy deposit, whi upon analysis, provesto be a carbonate. Be this as it may, it is important for us to know, that waters with but carbonate of lime in solution may lead to injurious consequences under circumstances that were unknown heretofore. Reports b our foreign cotemporaries inform us that cases of this kind have occurred in Switzerland, since the firing of boilers with coal in that country has become more universal. Old as well as new Cornwell and Fairbairn boilers were seen to become red hot, while the water gage indicated several inches of water above the fire space. They got out of shape in such a way that they had to be removed and replaced by new ones. Satisfactory information upon the subject is due to Prof. Bolley, in Zurich, who in various instances was called upon as an expert. The first case occurred in the Canton of Zurich, The feeding water was hard, but otherwise pure ; it contained but traces of organic matter and no sulphates. The mineral ingredients left behind, upon evaporation were found to consist of 81'84 per cent of carbonate of lime. It had settled as a white gray powder and in considerable quantities. If thrown upon water it remained floating upon it ; it did not get moist, and remained dry even when in contact with boiling water for some time. When exhausted with ether, a small amount of fatty matter separated, and this gave the clue to the disturbance mentioned. This pulverulent deposit covered the boiler plate to the hight of several inches, so that the water could not ccme in contact with it. The fatty matter was sufficient to surround the particles of the carbonate of lime with a thin layer, in this way causing them to float upon water if this was not subjected to pressure. Whence did this fatty matter originate ? At the very beginning it had been supposed that it came from the waste water of a neighboring bleaching establishment that flowed in the river a short distanceabove the spot where the feeding water was taken. Indeed, on examination, it was fpund that the bleaching liquid contained a small amount of fat, but whence this was derived could not be ascertained. Another case of this kind occurred in the Canton of Thur- govia. The deposit in question exhibited the same characteristics as described above, Upon being subjected to distillation in a retort with a small surplus of sulphuric acid, a very distinct odor of butyric acid could be perceived. One half a pound of the material in question was then boiled with distilled water and under addition of a little soda. In this way an alkaline solution was obtained with the fatty substance in solution. On filtering it and adding some muriatic acid butyric acid could also be perceived. At the same time small fat globules were recognized that did not disappear on diluting with water; on taking them up with ether, and evaporating, an odorless oily substance was left behind. When Bolley had recognized butyric acid, the opinion was entertained by him that it originated from the water, as this acid i& often met with in water arising from peat moors. But when he had detected fat, of which butyric acid is a constituent part, this opinion was abandoned, and now it was ascertained that the condensing water served to feed the boiler. The fat was probably derived from the lubricating oil. When some soda was added to the feeding water no dry deposit was obsrrved, and this was also the case when the condensing water was not employed for feeding. At any rate it is important to know that a small amount of fat in water that contains earthy carbonates, but no sulphates, may produce a dry instead of a muddy deposit. However, it is quite strange that this was not observed before, as the inside of boilers is sometimes rubbed over with fat, which is supposed to protect them from incrustations. With regard to the fuel, it is self-evident that it can not have any influence upon the formation of deposits. However the plates will become sooner red hot when coal instead of wood is used. It may yet be remarked that recent investigations have revealed the fact that butyric acid is of a more common occurrence in the soil and in water than hitherto supposed. Pierre detected this acid in soil that had not been fertilized for four years; it was also met with in the pond of a farm. On examination it was discovered that it had originated from putrescent sugar beets in which it often appears. Besides, it is known that straw and the food of cattle yield sugary elements that are more or less convertible into this acid. Several cases of similar powdery deposits have recently come to our knowledge in this country ; and we have received several specimens corresponding almost exactly to those described as having occurred in the boilers in Switzerland, and probably resulting from the same causes.
This article was originally published with the title "New Facts about the Formation of Deposits in Steam Boilers"