Composition and Value of Guano. 



229 



cipitation of the earthy phosphates does not give a perfect determination 

 of the phosphoric acid ; for, besides the phosphates of lime and magnesia, 

 which have the composition of bone-earth, there is in guano more or less 

 of the phosphates of potash and soda. The addition of ammonia does not 

 always cause a very uniform precipitate of phosphate of lime, the phosphoric 

 acid of the potash salt being more or less carried down with the salt of lime. 

 Phosphoric acid is therefore sometimes present in the liquid after this 

 precipitation. For ordinary commercial purposes the result is, however, 

 sufficiently accurate. 



The nitrogen analysis is conducted in the usual way, the guano being 

 burnt with soda-lime and the resulting salt of ammonia weighed as the 

 double platinum salt. Of the accuracy of this method there can be no 

 doubt, but it may be satisfactory to mention some cases where the analysis 

 of a specimen has been repeated with confirmatory results. Two nitrogen 

 analyses were made of specimen 14 in the third table : — 



1st analysis gave 16*46 per cent, of ammonia. 



2nd „ 16-75 „ 



Two analyses of specimen 16 : — 



1st analysis gave 16*93, per cent, of ammonia. 



2nd „ 16-70 



Two of specimen 34 : — 



1st analysis gave 17*37 per cent, of ammonia. 



2nd „ 17-69 „ 



Two of specimen 36 : — 



1st analysis gave ..... 16*79 per cent, of ammonia. 

 2nd „ 16*85 „ 



Two of specimen 37 : — 



1st analysis gave 16- 97 per cent, of ammonia. 



2nd „ 16*93 „ 



Very many other instances could be adduced to show that the results of 

 two analyses are the same, which in such cases is tantamount to a proof 

 of correctness in both. The duplicate analyses, specimens 34, 36, and 37, 

 were made by different persons, and are therefore more 'than ever satis- 

 factory. 



3. " Damaged Guano." — It is not unusual for a cargo of guano to suffer 

 from the action of the water by leakage in the vessel. If the quantity of 

 water thus entering is not great, it is absorbed by the outer portions of the 

 guano, that in the centre escaping altogether. The importers set aside 

 this portion, which is sold, according to its degree of wetness, at a reduced 

 price. 



The following are the proportions of water and ammonia in two speci- 

 mens of damaged guano sent to me by the importer : — 



W T ater. Ammonia. 

 1st Specimen, ship " Commerce" . . 80-68 per cent. . . 12-62 per cent. 

 2nd „ ship unknown . • . . 33*13 .. 15*71 



By a calculation based upon the analysis of a sound specimen of the 

 cargo of the " Commerce," given in Table 6, it will be seen that the de- 

 terioration in value of the specimen is only slightly greater than to the 

 extent of the proportion of water thus added to it. There is, however, an 

 absolute loss, which is due to the escape of ammonia with watery vapour, 

 a fact which is always observable to the smell in guano ships which have 

 suffered leakage. 



