ANALYZING OF MARL. 311 



the progress of such solution. The addition of the muriatic acid 

 must be continued as long as it produces effervescence ; and but 

 very little after that eifect has ceased. The mixture should be 

 well and often stirred, and should have enough excess of acid to be 

 sour after standing thirty or forty minutes. (So much of the acid 

 as the lime combines with loses its sour taste, as well as its other 

 peculiar qualities.) 



The mixture now consists of: 1, the lime combined chemically 

 with muriatic acid, forming muriate of lime, which is a salt, and 

 which is dissolved in the water ; 2, a small excess of muriatic acid 

 mixed with the fluid ; and 3, the sand, clay, and any other insolu- 

 ble parts of the sample of marl. To separate the solid from the 

 fluid and soluble parts is the next step required. 



3d. Take a piece of filtering or blotting paper, about six or eight 

 inches square (some spongy and unsized newspapers serve well), 

 fold it so as to fit within a glass funnel, which will act better if its 

 inner surface is fluted. Pour water first into the filter, so as to see 

 whether it is free from any hole or defect j if the filtering paper 

 operates well, throw out the water, and pour into it the whole 

 , mixture. The fluid will slowly pass through into a glass under the 

 funnel, leaving on the filter all the solid parts, on which water must 

 be poured once or twice, so as to wash out and convey to the solu- 

 tion every remaining particle of the dissolved lime. 



4th. The solid matter left, after being thus washed, must be 

 taken out of the funnel on the paper, and carefully and thoroughly 

 dried then scraped off the paper and weighed. The weight, say 

 27 grains, being deducted from the original quantity, 50, would 

 make the part dissolved (50 27 =23) 46 per cent, of the whole. 

 And such may be taken as very nearly the proportion of calcareous 

 earth (or carbonate of lime) in the earth examined. But as there 

 will necessarily be some loss in the process, and every grain taken 

 from the solid parts appears in the result as a grain added to the 

 carbonate of lime, it will be right in such partial trials to allow 

 about two per cent, for loss, which allowance will reduce the fore- 

 going statement to 44 per cent, of carbonate of lime. 



5th. But it is not necessary to rely altogether on the estimate 

 obtained by subtraction, as it may be proved by comparison with 

 the next step of the process. Into the solution (and the washings) 

 which passed through the filter, pt gradually a solution of car- 

 bonate of potash. The first effector the alkaline substance, thus 

 added, will be to take up any excess of muriatic acid in the fluid 

 and next, to precipitate the lime (now converted again to carbonate 

 of lime), in a thick curd-like form. When the precipitation is 

 ended, and the fluid retains a strong taste of the carbonate of 

 potash (showing it to remain in excess), the whole must be poured 

 on another filtering paper, and (as before) the solid matter left 



