GUANO 749 



Hence it is obvious that whilst guano was selling at 111. per ton, it was more eco- 

 nomical and convenient to employ it than to make an artificial mixture of its chemical 

 constituents ; but now that the price has risen, it becomes a question whether it 

 will not be possible to produce an artificial compound having equal value as a 

 manure which will compete in price with the guano. 



Impurities and adulterations. In consequence of the high price of guano, the 

 great demand for it, and the ease with which the unwary farmer may be imposed 

 upon, guano is adulterated with various substances, and to a great extent. Impo- 

 sitions even have been practised by selling as genuine guano artificial mixtures, 

 made to look so much like guano that the farmer would scarcely detect it. The 

 writer recollects examining a guano which contained 50 per cent, of sand, and no less 

 than 25 per cent, of sea-salt ; and Dr. Ure gi^'es the following analysis of an article 

 sent to him, which had been offered to the public by advertisement as Peruvian guano, 

 which contained 



Common salt . . . . r . . . 32'0 



Sand * -.: -, ,. 28-0 



Sulphate of iron . . . ' . . ^* . ' ...' 6*2 



Phosphate of lime V- - 4'0 



Organic matter (from bad guano, to give it smell) . . 23'3 

 Moisture .-..!- 7*5 



100-0 



In fact, so numerous and various are the tricks played with guano, that unless a 

 sample is submitted to a skilful chemist for analysis before purchase, we would 

 strongly recommend the agriculturist to purchase of no one but dealers of unquestion- 

 able honour. 



Professor Johnstone observes : ' -Four vessels recently sailed hence for guano 

 stations, ballasted with gypsum, or plaster-of-Paris. This substance is intended for 

 admixture with guano, and will enable the parties to deliver from the vessel, a nice- 

 looking and light-coloured article. The favourite material for adulterating guano 

 at the present moment is umber, which is brought from Anglesea in large quantities. 

 The rate of admixture is, we are informed, about 15 cwts. of umber to about 5 cwts. 

 of Peruvian guano, from which an excellent-looking article, called African guano, is 

 manufactured.' 



Analysis of Guano. 



The following is Dr. lire's method for the complete analysis of guano : 



1. In every case I determine, first of all, the specific gravity of the guano ; which I 

 take by means of spirits of turpentine, with a peculiar instrument contrived to render 

 the process easy and precise. If it exceeds 1*75 in density, water being ro, it must 

 contain sand impurities, or has an excess of earthy phosphates, and a defect of azotised 

 animal matter. 



2. I triturate and digest 200 grains of it with distilled water, filter, dry the in- 

 soluble matter, and weigh it. 



3. The above solution, diffused in 2,000 gr. measures, is examined as to its specific 

 gravity, and then with test-paper, to see whether it is acid or alkaline. 



4. One half of this solution is distilled along with slaked lime in a matrass con- 

 nected with a small quintuple globe condenser, containing distilled water, and immersed 

 in a basin of the same. As the condensing apparatus terminates in a water-trap, no 

 part of the ammonia can be lost ; and it is all afterwards estimated by a peculiar 

 meter, whose indications make manifest one hundredth part of a grain. 



5. The other half of the solution is mixed with some nitric acid, and divided into 

 three equal portions : 



a, the first portion, is treated with nitrate of baryta, and the resulting sulphate of 

 baryta is collected, ignited, and weighed. 



b, the second portion, is treated with nitrate of silver, and the resulting chloride of 

 silver ignited and weighed. 



c, the third portion, has a certain measure of a definite solution of ferric nitrate 

 mixed with it, and then ammonia in excess. From the weight of the precipitated sub- 

 phosphate of iron after ignition, the known amount of oxide used being deducted, the 

 quantity of phosphoric acid in the soluble portion of the guano becomes known. 



d, the three above portions are now mixed, freed by a few drops of dilute sulphuric 

 and hydrochloric acids from any baryta and silver left in them, and then tested by 

 nitrate of lime for oxalate of ammonia. The quantity of oxalate of lime obtained de- 

 termines that point. 



