On the Fire and Choak-Daiiips of Coal JMines. 2(31 



The combinations of the second are the greater part in- 

 soluble m water ; that which it forms particularly with 

 lime is not sensibly soluble but bv the aid of an excess of 

 acid, and its existence in nature is not so frequent as that 

 of the acetic arid ; and since the lime which is found in 

 transparent gums has been incontestibly dissolved in the 

 juices of the vegetables which furnished the.-e substances, 

 it is much more probable that this earth is there combined 

 with the acetic acid than with any other. 



It is very probable that the small quantity of potash which 

 I found in the ashes of the burnt gums is united to the same 

 acid, which would explain why these substances are so sen- 

 sible to humidity, and soften themselves so as not to be 

 pulverizable. 



I am, however, very much disposed to believe, that in 

 (pertain opake adraganth gums diificult to dissolve, and 

 Vv bieh give much lime bv incineration, this earth is there 

 combined with the malic acid. I have had occasion to 

 examine lately a gum collected by M. Pallissot-Bauvois on 

 the nopal of cochmeal, which was opake, swelled itself in 

 water, but did not dissolve in a homogeneous manner, and 

 which gave eight per cent of lime. 



As the sap of rdl the cactus which I have submitted to 

 anaJvsis has afforded me quantities n^ore or less considera- 

 ble of the acidulous malate of lime, one may presume, with 

 sufficient reason, that the kind which nourishes the cochi- 

 neal contains it also; and that it is the presence of this salt, 

 proceeding from the vegetable when dissolved in the sap 

 with the gum, which gives it its opacitj', and hinders its 

 solution in water. 



It results at least from these experiments, that the gums 

 contain, 1. A calcareous salt, niost frequentlv the acetate 

 of lime : iJ. Sometimes a inalate of lime with excess of 

 acid: 3. Phosphate of lime: 4. Iron, which is probably 

 united to phosphoric acid. 



LI. A proposal for clastroi/ii/g the Fire- and Clioak-Damps 

 (f Coat AFuiC'i; and their Production explained on the 

 Principks of modern Chemist nj: addressed to the Owners 

 and yigcnis of Coal Works, &jc. 



X UK subjoined remarks arc extracted from a little tract 

 which prol'esses only to hold out a siiort explanation of 

 well known facts, in the hope of seeing them conducive to 

 save human beings whose labours are useful to the com- 

 K 3 inuuitv. 



