April 1908.] 



337 



Scientific Agriculture* 



in each sample was then determined and 

 the results are set out in the following 

 table : — 



Time of Exposure 



Undried. 



Dried. 



j Weight. 



Nitrogen pet- 

 cent on Origi- 

 nal Weight. 



| Weight. 



j Nitrogen per 

 cent on Origi- 

 nal Weight. 





Gram. 





Gram. 





Starting 



1-000 



17-24 







After 1 week ... 



1-669 



16-87 



1-231 



16-01 



2 weeks . . . 



1-734 



16-30 



1-240 



15- 88 



',, 3 „ ... 



1-793 



16-18 



1-259 



15-26 



„ 4 •• 



1-859 



15 97 



1-269 



15-77 



„ 5 ... 



2-234 



15-85 



1-289 



15-89 



„ 6 „ ... 



2 069 



16-17 



1-278 





7 „ 



2-431 



16-24 



1-298 



15-13 



„ 8 „ .. 



2-508 



16-21 



1-295 



14-92 



„ 9 „ - 



2-802 



15-75 



1-296 



14-52 



iu ,, ... 



3-235 



16-03 



1-396 



14-69 



These results show that the first action 

 of slaking the free lime in the crude 

 c-yanamide takes place very quickly 

 when the material is exposed in a thin 

 layer to an atmosphere saturated with 

 moisture since the weight ris^s 67 per 

 cent, in the wet condition and 23 per 

 cent, in the dry condition during the 

 first week's exposure. At the same time 

 there is a slight loss of ammonia, though 

 this loss is almost covered by the experi- 

 mental error inherent in drawing small 

 samples from a powder of variable com- 

 position like cyanamide, the difference 

 being little greater than that found be- 

 tween consecutive samples drawn for 

 analysis from the original manure. 



With further exposure the cyanamide 

 continues to absorb water until in the 

 end it runs down to a wet paste; further 

 losses of ammonia in the wet state, are, 

 however, small, being in the final sam- 

 ple only 7 per cent, of the total nitrogen 

 with which the material started. The 

 weight after drying increases but little 

 in the latter part of the experiment, be- 

 cause the main reaction causing an in- 

 crease of weight— the slaking of the free 

 lime — is completed in the first week. 

 The losses of nitrogen in the dried sam- 

 ple increase steadily and amount to 

 about 2 per cent, after the tenth week. 

 These losses are due to the volatilisation 

 during the drying of any ammonium car- 

 bonate that has formed. 



Other experiments on these lines were 

 made, in which the exposed cyanamide 

 was dried iu a current of air that was 

 afterwards passed through acid to absorb 

 any ammonia volatilised; they confirm 

 43 



the results set out above and show that 

 the action in the first week is almost 

 wholly a slaking of the free lime attended 

 by a slight production of ammonia which 

 is only volatilised as long as the material 

 remains dry. After the slaking is com- 

 plete the material begins to get damp 

 and may form a cake; in these later 

 stages larger quantities of free ammonia 

 are produced but only volatilised on dry- 

 ing. 



It should be borne in mind that these 

 are extreme cases and that changes of 

 the magnitude of those taking place in 

 the first week would only occur in a 

 manure store after a long time, so slow- 

 ly would mositure reach the material in- 

 side the bags. It is wellknown that 

 ground quicklime itself can be stored in 

 bags for some time without serious 

 change. To determine the extent of the 

 change taking place in practice, bags 

 containing 56 lb. each of cyanamide 

 sulphate of ammonia and nitrate of soda 

 were placed on the floor of the manure 

 shed on 1st August and weighed again 

 on 21th August and October, 



Aug. 1st. Aug. 24th. Oct. 14th. 

 lbs. lbs. lbs, 



Cyauamide ... 6 ... 57| 58} 



Sulphate of ammonia 56 ... 56J ... 57j? 

 Nitrate of soda ... 56 ... 55f ... 5i\ 



On 24th August the cyanamide was 

 powdery and in good condition, by 14th 

 October one corner of the bag had burst 

 owing to swelling from the slaking of 

 the lime ; the total gain of weight, how- 

 ever, is only 2| lb., or about 5 per cent. 

 Now as under conditions of maximum 

 exposure and complete slaking a gain of 

 67 per cent, of moisture had only been 

 attended by a loss of 0-67 per cent, of 

 nitrogen, the loss of ammonia when cya- 

 namide had been stored in a bag and had 

 only gained 5 per cent, in weight would 

 be imperceptible, since we may assume 

 that the loss will be in proportion to the 

 extent of slaking. That the atmosphere 

 of the manure shed had been damp is 

 shown from the fact that the sulphate 

 of ammonia had also gained in weight 

 and caked a little, while the bag of nitrate 

 of soda had become soaking wet, so that 

 the floor beneath was saturated and a 

 considerable loss of material took place. 



It may be concluded that while cal- 

 cium cyanamide will gradually slake 

 and swell, and suffer a small loss of am- 

 monia on exposure to damp air in bags, 

 yet under ordinary working conditions 

 these losses will be inappreciable, and 

 the manure is no more difficult to store 

 than other artificical manures used by 

 the farmer. 



(2) The manufacturers state that they 

 now take special precautions to leave no 



