86 Properties of Wood Ashes. 



parently across the semiglobule, and continued thus to play in 

 the most lively manner from various points in rapid succession 

 until inflammation ensued. This pretty miniature pyrotechny 

 can only be seen in the dark. 



Hygrometric Powei^ of Wood Ashes* — One hundred grains of 

 dried ashes were lightly spread over an area of sixty square inches, 

 and were exposed with due caution in the shade for twenty four 

 hours, when the noon temperature was 62°, and the air clear and 

 calm. In this time they gained no weight ; continued exposure 

 for seventy two hours enabled them to gain .55 of a grain. But 

 when the temperature was near the freezing point at noon, they 

 frequently gained in eight to twenty four hours from .66 to 1.66 

 of a grain. A fine sponge was converted into a sensitive hy- 

 grometer by saturating it with a solution of carbonate of potash, 

 and drying it at 170°. Thus prepared the sponge gained from 

 thirteen to forty four per cent, more than the ashes, and it assist- 

 ed rxie in making out the following deductions from eighteen ex- 

 periments on the hygrometric properties of ashes. 1. They absorb 

 atmospheric vapor more rapidly at a low than at a high tempera- 

 ture. 2. They do not cease to act hygrometrically at a tempera- 

 ture considerably below the freezing point. 3. The range of per 

 centage of increase is from to 1.66. 4. Different parcels 

 of ashes possess different degrees of hygrometric power. This 

 is owing perhaps to the varying quantity of potash present. 



Carho7iaceous Dust in Ashes.— It became interesting to ascer- 

 tain how much, if any carbon, in a pulverized state, existed in 

 ashes. For this purpose I employed sundry rather rude methods, 

 now to be mentioned. 1. By pouring a sufficient quantity of 

 sulphuric acid on sifted ashes, to moisten them, much caloric 

 was disengaged, and a white paste formed, in which black parti- 

 cles were very obvious. These particles washed and crushed 

 between the teeth, produced the peculiar sensation of breaking 

 charcoal. On diluting this paste with a large quantity of water, 

 a milky mixture (sulphate of lime) was obtained, in which the 

 black particles rapidly subsided. All the black sediment, how- 

 ever, was not coal. 2. One thousand grains of sifted ashes were 



* Your note appended to a former communication from me, requires that I should 

 say now what I ought to have said while penning that communication, that hy- 

 grometric dampness was expelled from the ashes in the experiment referred to. 



