108 



CHEMISTRY. 



secticide on growing plants has made the ques- 

 tion of its effects on the soil and through this 

 on vegetation an interesting and important one. 

 Some experiments on the subject made by Mr. 

 Wm. McMurtrie, and reported in the monthly 

 bulletin of the Agricultural Department, would 

 seem to show that, from the quantities com- 

 monly employed, no bad effects need be ap- 

 prehended, but that larger quantities diffused 

 through the soil would be decidedly injurious. 

 The points to be determined were : 



1. If applied to the soil, are arsenical compounds 

 absorbed and assimilated by the plant? 2. If so 

 absorbed and assimilated, can a sufficient quantity 

 be taken up to injure the health of the consumer ? 



3, If not taken up by the plant, is the latter injured 

 by the presence of the arsenic in the soil ? 4. If in- 

 jurious to the plant, how much may the soil contain 

 before the injury is apparent? 



The experiments consisted in mixing with 

 equal quantities of garden-soil contained in 

 pots a regularly-increasing quantity of some 

 soluble arsenical compound, and then planting 

 peas therein and noting the results. Each of 

 fifteen pots received 91.5 cubic inches of soil. 

 One pot was left uncontaminated and marked 

 ; with the soil of another pot marked 0.1, one- 

 tenth of a gramme of Paris-green was thorough- 

 ly intermixed; another pot marked 0.2 received 

 two-tenths of a gramme of the same poison, 

 and so on, until the soil in the tenth pot con- 

 tained one gramme of the Paris-green. Pots 

 11, 12, 13, 14, contained respectively 2, 3, 4, 

 and 5 grammes of the poison. A second series 

 containing arsenic in the form of arsenite of 

 potash, and a third poisoned with arseniate of 

 potash, were prepared in a similar way. Peas, 

 carefully selected, were now planted in each 

 one of the pots, and each series in its proper 

 order set by itself in a place suitable for the 

 growth of the plants. When sufficient time 

 had elapsed to obtain a comparison of effects, 

 it was found that in the case of the Paris- 

 green series of pots the plants in 1, 2, 3, and 



4, were about equal in size and appearance to 

 the plant standing in the non-poisoned soil, or 

 in the pot marked 0. On the other hand, in 



5, 6, 7, 8, 9, 10, and 11, there was a distinct 

 though gradual falling off in size and vigor, 

 while in 12, 13, and 14, nothing appeared 

 above the surface of the soil. In the series 

 poisoned with arsenite of potash the effect ap- 

 peared to be more immediate, the apparent 

 falling off beginning in pot 3, while in the four 

 pots containing the larger quantities of poison 

 nothing came up. The effect was more marked 

 still in the series in which arseniate of potash 

 was present, pot 1 as compared with that 

 marked showing distinctly the influence of 

 the poison, yet the plants came up in all but 

 the three containing the larger proportions of 

 the arseniate. 



All the plants were subsequently examined 

 for arsenic, in the ordinary way, but not a trace 

 was found. The author thus sums up the re- 

 sults of the investigation. 



With these facts before us, and without consider- 



ing what might be the result of a series of experi- 

 ments continued through a number of years, we must 

 conclude that plants have not the power to absorb 

 and assimilate from the soil compounds of arsenic, 

 and that though arsenical compounds exert an in- 

 jurious influence upon vegetation, yet this is without 

 effect until the quantity present reaches for Paris- 

 green about 900 pounds per acre ; for arsenite of po- 

 tassa, about 400 pounds per acre ; for arseniate of 

 potassa, about 150 pounds per acre. 



Improved Manufacture of Sulphuric Acid. 

 Since the adoption of Gay Lussac's method, 

 which apparently left little to be desired, either 

 in point of accuracy or economy, but slight ad- 

 vance has been made in the manufacture of 

 sulphuric acid until quite recently. In order 

 the better to understand the character of the 

 later improvements, it will be necessary to 

 give the main features of the process now in 

 general use. This, as commonly carried on, is 

 as follows: 



A sulphur mineral is burnt upon the hearth of a 

 furnace in the presence of a sufficient supply of air; 

 the sulphurous acid so formed is sent forward into a 

 large leaden chamber, being made to carry with it 

 in its passage a quantity of nitrous fumes, which 

 fumes, in the chamber, act as the vehicle or carrier 

 for the transference ot the oxygen from the air to 

 the sulphurous acid, the latter, consequently ? be- 

 coming oxidized to form sulphuric acid. At differ- 

 ent points of the chamber jets of steam are intro- 

 duced for two purposes : first, to supply the proper 

 amount of water for the hydration of the sulphuric- 

 acid compound ; and. second, to cause the precipita- 

 tion of the so-formea acid on the floor of the cham- 

 ber, whence it may be run off. For a long time 

 it was considered that a certain heat in the chamber 

 should be maintained, and that the steam thus intro- 

 duced also effected this result; this has since, how- 

 ever, been proved to be erroneous. In every 2,000 

 tons of acid formed in the chamber there are con- 

 tained about 1,000 of water, which water, seeing that 

 none is introduced in any other form, must have 

 been obtained by the condensation of steam. 



The improvements referred to consist in the use, 

 in the place of steam, of what has been called " pul- 

 verizea" or " atomized" water or spray, this f-priiy 

 being injected into the chambers in the place of the 

 steam-jets. Dr. Sprengel, whose invention this is, 

 lias been working at the matter for a considerable 

 time, and has demonstrated the perfect success of 

 the improved arrangement at the Lawes Chemical 

 Manure Company's works, Barking, England. It 

 would seem that, beyond the chief advantage, that 

 of the saving of fuel, there are other advantages to 

 be obtained oy this method of working. The cham- 

 ber, for example, is much cooler without the use of 

 the steam, and it is found that the yield of acid is 

 better under such circumstances, while at the same 

 time the chambers can be made to do more work, as 

 a greater quantity of the gases will be contained in 

 them at a given time, owing to such gases occupying 

 a less volume at the reduced temperature. The 

 water-spray is produced by the use of a small quan- 

 tity of steam, which is made to escape from a plati- 

 num jet, under a pressure of about two atmospheres, 

 into the centre of a flow of water. 



Twenty pounds of steam used in this way will 

 convert 80 Ibs. of water into a fine mist, the actual 

 weight of which, issuing from a jet of the above size, 

 amounts to about one-third of a ton in twenty -four 

 hours. These jets are placed in the sides of the 

 chambers about forty feet apart, being supplied with 

 water from a tank above. The saving of coal by 

 this arrangement amounts to about two-thirds of 

 that formerly burnt, and from statements made by 

 Messrs. Lawes it would appear that they have al- 



