THE CALCARIMETER. 253 



simply three marks upon it. The capacity of the tube from 

 the point marked a to the lower extremity is equal to the 

 capacity of 50° of the other tube, and the other two marks 

 correspond to ten and five. The use that is made of these will 

 be hereafter explained. 



Manner of performing the analysis. — Being furnished with the 

 two tubes, the two fluids, a capsule or other convenient vessel, 

 a small piece of glass rod a few inches long, a wine-glass, and 

 a piece of litmus-paper, a portion of which has been reddened 

 by an acid, we proceed as follows : Weigh out fifty grains of the 

 substance to be examined, place it in the capsule, and add to 

 it about one ounce of water ; fill the instrument last described 

 up to the highest mark upon the stem with the acid. This is 

 done by holding it between the thumb and fore-finger, having 

 the little finger applied to the lower opening. After the acid 

 is poured in, before withdrawing the finger, introduce the cork, 

 and place the fore-finger of the other hand upon the opening 

 of the tube on the cork, for the purpose of preventing the 

 liquid flowing out when the lower opening is left unprotected. 

 After seeing that the acid stands exactly at the mark it is 

 allowed to flow gradually upon the substance. After all the 

 action has ceased, stirring it toward the end to insure this 

 result, we fill the graduated tube with the solution of ammonia, 

 in the same manner as we did the last, and let it fall gradually 

 upon the mixture of acid and calcareous substance, arresting 

 at will the progress of the flow by simply placing the finger 

 upon the tube in the cork. This instrument should always be 

 transferred to the left hand and held in an inclined position. 

 During the addition of ammonia the mixture should be well 

 agitated with the glass rod, and occasionally tested by bringing 

 a little of it upon the extremity of the rod in contact with the 

 litmus-paper, and as soon as it ceases to turn this paper red, 

 or begins to turn the red part of it blue, the experiment is 

 completed, and we now look at what number of degrees the 

 fluid stands in the tube, and we are furnished with the per- 

 centage of carbonate of lime contained in the calcareous sub- 

 stance examined.* We may be saved the trouble of testing 



*If magnesia happens to be present it will be estimated as lime; but this 

 will very seldom be a cause of error, as it exists very rarely in calcareous 

 manures, for which this instrument is particularly intended. 



