some varieties of South American Guano. 139 



Now Dr. Fownes supposes that the uric acid of the urate of 

 ammonia combines with eight equivalents of water and two of 

 oxygen from the air, and produces four equivalents of oxalate 

 of ammonia and two of carbonic acid, which of course unites, 

 although it is not so stated in the note I refer to*, with the 

 equivalent of ammonia before combined with the uric acid, 

 producing the bicarbonate of ammonia, not the most volatile 

 nor soluble of its salts, and which, if formed, surely ought to 

 be found in every sample of guano. Now various specimens 

 of guano have been examined, seven in number, in what we 

 may suppose to be all the progressive stages of this conver- 

 sion of the urate into the oxalate of ammonia; one containing 

 uric acid, urate of ammonia and oxalate of ammonia ; a second 

 containing the two salts only ; and others in which the uric 

 acid and urate of ammonia have wholly disappeared, and oxa- 

 hite of ammonia alone remains : yet in no one of these speci- 

 mens of the guano has the substance, bicarbonate of ammonia, 

 which is required by Dr. Fownes's theory, been detected ; its 

 presence would not necessarily have proved the theory to be 

 correct, as it might fairly and possibly be attributed to the 

 decay of azotized animal matter : but I respectfully submit 

 that the absence of this ammoniacal salt pi'oves this hypothesis 

 of the conversion of urate into oxalate of ammonia to be 

 erroneous. After the opinions I have uttered respecting the 

 employment of hypothetical deductions, it is certainly vastly 

 inconsistent on my part to have recourse to them, but it will 

 tend to prove the truth of my former remarks on the readiness 

 with which a theory in organic chemistry may be constructed, 

 when no inconvenient nor insurmountable facts are opposed 

 to it. In detailing this theory of the conversion of the urate 

 into the oxalate of ammonia, I am more than indifferent to 

 its fate; for gladly will I lend a helping hand to put an ex- 

 tinguisher upon it, if one based upon the actual and experi- 

 mental conversion of the one salt into the other, a result I 

 have endeavoured in vain to effect, is propounded. 



Since Coindet's observation, that the uric acid in the excre- 

 ment of birds existed as binurate of ammonia, the equivalent 

 number of uric acid seems by general consent to have been 

 doubled, so that this acid salt, according to Coindet's view, 

 must now be considered as neutral urate of ammonia. Like 

 Dr. Fownes's, my hypothesis of this conversion is an absorption 

 of water and very slight oxidation, differing from his only in 

 the proportions of these convenient substances, and in the 

 conversion of the urate into the oxalate of ammonia without 

 the formation of carbonate of ammonia or any other secondary 

 ♦ Memoirs of Chemical Society, part 3, p. 38. 

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