MECHANICS AXD USEFUL ARTS. 49 



x 



grammes of sal ammoniac into tnis boiler, after having been cleaned of all 

 previous incrustations. Four months after ward, I submitted to an exami- 

 nation the sides of this boiler, and I found a tolerably regular accumula- 

 tion of incrustations on the vertical sides, while above the furnace this 

 crust was much less. Its thickness was evidently less everywhere than 

 usual, aaid nevertheless, during all this period, it had been heated on the 

 average 14 hours per day. The boiler was cleaned anew, and about 4. 5 

 pounds of incrustations removed. I at once commenced a new trial, and 

 as I did not know exactly the proportion of salt necessary to completely 

 prevent the evil, I resolved to double the former trial, and to use 200 

 grammes, which, was thrown twice a week into the boiler. After more 

 than five months of work, there were still some incrustations, and princi- 

 pally, as in the first trial, on the vertical sides ; but the experiments go to 

 show that, by the use of this salt, incrustations may be very much dimin- 

 ished, sfnd perhaps totally prevented, and it is of great importance to pur- 

 sue these experiments further." 



The following is for the most part an abstract of a recently published 

 work by Dr. Eisner, German : 



On the means hitherto employed in preventing the production of scale 

 in steam-boilers, with the addition of some original observations upon this 



subject. 



Potatoes. Of these, one- fiftieth of the weight of the water is said to be 

 sufficient to prevent the incrustation. According to Eisner, crusts already 

 formed are not removed by potatoes. The action is mechanical ; the cal- 

 careous particles, when separated, becoming coated with the slimy matter 

 of the potatoes, which prevents their forming a coherent deposit. 



Fatty Oils, Talloic. Oil, when poured into the water, is Said to prevent 

 incrustation. According to Kennedy, the inside of the boiler should be 

 well rubbed with a mixture of three parts of black lead and eighteen parts 

 of tallow. Newton recommends one part of tallow, one part of black lead, 

 and one- eighth part of powdered charcoal. The statements as to the 

 degree of protection afforded by this agent are satisfactory. 



Sawdust. A patent was obtained in this country about eight years ago, - 

 for the exclusive use of mahogany sawdust introduced into the boiler. 

 Indian meal introduced into the boiler has aln) been tried with success. 

 Ira Hill replaced the mahogany dust by oak~ dust, and any other wood 

 will serve equally well. The disadvantages of this prevention is the 

 readiness with which the sawdust may be carried into the pipes, cocks, 

 valves, etc., where it might produce evil consequences. The action of the 

 sawdust is also mechanical. 



Clay, free from sand, and worked up "with water, is recommended by 

 Chaix. Aldefeld found that this agent prevented the formation of scale ; 

 but that, 011 the other hand, it produced a slimy coating in the pipes, and 

 rendered the steam cylinder rough. Its action is also mechanical. 



Ammoniacal Compounds. Kitterbrand, in 1844, patented certain amrno- 

 niacal compounds, especially muriate of ammonia. Eisner regards this 

 3 



