126 Mr. Denham Smith on the Composition of 



acetic acid be in too great excess, more than completely suf- 

 ficient to redissolve the precipitate produced by ammonia, 

 the clear solution, although containing no magnesia, will at 

 times, as I have found, give indications of the existence of 

 lime on supersaturation with ammonia ; but the quantity under 

 such circumstances held in solution is too small to be of im- 

 portance except in cases where a scientific point is involved. 

 Where oxalate of lime is in solution together with the mag- 

 nesian and calcareous phosphates, this process requires some 

 modification, which it may be better to explain in the details 

 of the mode I have adopted in the analysis of guano, than at 

 present — that recapitulation may be as much as is possible 

 avoided. 



It may be advantageous here to describe the mode of ana- 

 lysis pursued in the examination of these samples of guano, 

 as each analysis, in fact, consists of three separate ones, viz. 

 of those portions soluble in cold water; the substances which 

 dissolved on boiling the residue insoluble in cold water, in 

 abundance of water ; and the portion which remained inso- 

 luble in either menstruum. This division I found to be a very 

 convenient one, as the solutions obtained were far less com- 

 plex than if the portions of the guano soluble in water cold and 

 hot, and in acids, had been mixed together; and it of course 

 gives a pretty correct idea of the salts as they actually are 

 presented to the roots of plants manured with guano. My 

 reasons for combining the bases and acids as I have done in 

 the results of these analyses are, that in some cases the propor- 

 tional quantities of acid and base have tallied, and also that I 

 have obtained by crystallizing the hot and cold solutions, 

 oxalate of ammonia, oxalate of soda, muriate of ammonia, 

 chlorides of potassium and of sodium, sulphates of soda and 

 potash, urate of ammonia and free uric acid, from the various 

 samples of guano ; and also that by microscopic examination 

 crystals of the chlorides and of sulphate of soda have been 

 readily observed in the mass of the guano. As I have also 

 given the amount of bases and acids obtained without re- 

 ference to the state of combination in which they exist, those 

 who differ from me in this respect, can combine them as they 

 think proper. 



The mode adopted for determining the respective amounts 

 of the fixed alkaline bases is open to many objections. It is 

 complex ; a very slight error in weighing is liable to consi- 

 derably vitiate the result: if the whole numbers I have 

 adopted as representing the combining equivalents of the va- 

 rious acids and bases are incorrect, so also must the results 

 be. On the other hand, I have tried this method upon an 



