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234 [AssemBLy, No. 33.] 
When the ashes of a tobacco of good burning quality are washed 
in cold water, some carbonate of potash is always found in the solu- 
tion. We do not find this when the tobacco is not combustible. The 
soluble potash is then entirely in the condition of the sulphate or the 
the chloride.. There is then a relation between the combustibility and 
the presence of carbonate of potash (the tobacco containing no soda). 
Or the carbonate is a product, in fact, of the combustion. ‘The rela- 
tion shown then is due to the compounds from which the carbonate is 
derived; that is to say, to the nitrates and to the organic salts of pot- 
ash. ‘The nitrate may be laid entirely aside. In fact, tobaccos-that 
contain much of it are incombustible,-while others that contain none 
of it burn perfectly. The efficiency of the organic salts, however, 
can be directly demonstrated. 
When in an incombustible tobacco we incorporate a certain propor- 
tion of malate, citrate, oxalate or tartrate of potash sufficient so that 
the ashes will contain some alkaline carbonate, the tobacco becomes 
combustible. On the other hand, when we incorporate in a combusti- 
ble tobacco a certain proportion of sulphate or chloride of calcium or 
manganese, so that the ashes contain no more carbonate of potash, the 
tobacco becomes incombustible. In this case the larger part of the 
organic salts of potash has been converted by double exchange into 
organic salts of lime and manganese. 
It is certain then that the sign of combustibility (burning quality) , 
is the presence of carbonate of potash in the ashes; that its absence 
is the sign of incombustibility.. That suffices to guide the cultivator. 
He knows now that the soil should furnish a quantity of potash suffi- — 
cient to produce combustibility, and that it must be applied if want-* 
ing; but under what form and combination? ‘These new questions 
have been resolved by direct trials in culture in fields almost desolate 
of potash. It has been found 7 | 
1. That the chloride of potassium (muriate of potash) should be 
rejected ; the chlorine passes with the potash into the tobacco and the 
alkali thus neutralized does not concur to the formation of organic 
acid salts. 
2. That the sulphate agrees perfectly ; that the potash is assimi- 
lated to the exclusion of the acid. 
The nitrate and the carbonate also are entirely suitable, but their 
price is too high. ‘That of the sulphate is, on the contrary, now quite 
reasonable. 
In regard to the quantities to employ, these are evidently variable 
according to the previous treatment of the soil, and its absorbing 
power for alkali, etc. Direct trials alone should guide the cultivator 
in such matters. The potash is not lost in the soil so that when a soil 
has acquired a sufficient quantity of alkali to produce combustible to- 
bacco, the condition may be kept up by supplying acalculated amount 
equal to that taken off in the harvest. ‘Too much potash causes the ~ 
leaf to burn with a black ash. = & : 
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