Bleachi 



Soda. 



Barilla. 



BLEACHING. 581 



ng. to take a given quantity of the alkali, and dissolve it its use is now almost universally given up, potash Bleaching. 



' in twice its weig' t of boiling water, stirring the mix- being substituted in its stead. v ' 



ture during the solution of the salt ; while yet warm, 3d, Kelp would be unworthy of notice, were it Kelp, 



it must be filtered through unsized paper. When all not that it is still recommended by some as a detcr- 



the liquor has passed through the filter, a very small gent in bleaching. .. 



quantity of cold water is gradually poured on the As at present manufactured, kelp is very inferior 

 saline residuum on the filter, in order to wash out the in this respect : The very best Scotch kelp never con- 

 remainder of the alkali. The undissolved salt remain- tains above 7 or 8 per cent, of mineral alkali, but 

 ing on the filter, is sulphate of potash, which must more commonly from 3 to 5 per cent. Considering 

 be carefully taken off, dried and weighed, in order to the other impure substances contained in kelp, it is 

 ascertain its quantity. To determine whether any at present unworthy of attention. But there is no 

 commofl salt is contained in the alkali which has been doubt, that if proper methods were adopted for the 

 filtered, evaporate the clear solution a little in a sand manufacturing of it properly, it may be very much 

 bath, and set it in a cool place for 24 hours ; at the improved in quality. In the present rude manner in 

 end of which time, any common salt it may contain, which it is made, the marine plants called Fucus 

 will be found crystallized in the form of regular cubes Serratus and Fucus Vesiculosus of Linnxus, being 

 at the bottom of the vessel. The sulphate of potash cut at midsummer, and dried by the sun and air, are 

 and common salt being dried, weighed, and deducted burnt in holes made in the sea beach : when a large 

 from the weight of the crude alkali employed, will portion of it is burnt together, part of the salt fused 

 give the precise weight of the pure alkali it contains, by the strong heat combines with sand, and other 

 II. Pure carbonate of soda, or the mineral alkali, so earthy matters, and forms an imperfect glass. In a 

 much resembles the vegetable alkali, when used as an furnace properly constructed, with a graduated heat 

 agent in bleaching, that little difference is observable we have known kelp made of a quality far superior 

 in its effects when the strength of the alkaline leys to the very best of that which is made by the com- 

 and every other circumstance are the same. The mon process. 



high price at which soda has hitherto sold, fi#s pre- It has been suggested, that were the sea plants 

 vented its being generally used at the bleachlield ; from which the kelp is made, previously washed in 

 but since more economical processes are adopted in fresh water before they are dried, they would "thereby 

 the manufacture of it, and since it is made in a be freed from a large portion of the marine acid ad- 

 greater degree of purity, its introduction into the hering to them, which remains undeeomposed during 

 bleachfield will naturally follow. It is admirably cal- the burning of the plant when it is converted into kelp, 

 culated, as a detergent, for the finishing of the finer This theory supposes, that the plant, during the pro- 

 fabric of muslin ; it being ascertained beyond doubt, gress of its growth, has the power of decomposing the 

 that 6 ounces of pure carbonate of soda, together sea-water, and retaining soda as one of its component 

 with 10 ounces of soap, produce effects in bleaching parts : and that if this be the case, and if the corn- 

 equal to H pounds of soap, when used by itself. bustion of the plant were properly conducted, a salt 

 2d, Barilla, as imported from Alicant in Spain, is nearly equal in value to barilla would be the pro- 

 in large masses, of a dark gray colour. It usually duct. These facts may be easily proved by those 

 contains from 20 to 24 per cent, of pure mineral al- who have skill to ascertain, and opportunity to in- 

 kali, and never above 33 per cent, when in a state of vestigate, a matter which is of considerable national 

 the greatest purity. The remainder of the mass usual- importance. 



ly consists of sulphate and sulphite of soda, with a In order to ascertain the quantity of real alkali Real al- 



large proportion of charcoal and common salt. contained in the different detergent salts used in kali con- 



The best method of extracting the soda from ba- bleaching, M. Descroizilles sen. employed the me- tained ,a 



rilla, is to pound it, and fill a large wooden vat with thod belore mentioned, by saturating a given quan- dl ' Ferent 



it, the bottom of which has been previously covered tity of the alkaline salt with diluted sulphuric acid '* 



with straw, to act as a filter ; the vat is then filled the specific gravity of which was always the same, 



with cold water, which is allowed to remain for some After many thousand trials during the course of 



time to dissolve the salt. When sufficiently strong 25 years practice, the following are the mean results : 

 for use, the solution is run off at the bottom of the 



vessel by a stopcock, by which means it is freed Real Alkali 



from the charcoal and other impurities. Fresh water n a in 10 Parts. 



is again poured on the barilla, until the whole of the CSt Am f lcan P earl ashcs .' ' ' '.i^ 60 to 7S 



salt is dissolved. By this operation the soda is ex- Ca . U3tIC d ' U p0t asheS In reddlsh | G0 63 



traded, which being a very soluble salt, is easily dis- ,um P s > " * ' " '. " : * *i * 



solved by the water ; but, at the same time, the com- Second ditto ditto in gray lumps, . . 50 55 



mon salt, which is equally soluble, together with a ^: t ; ond , d,tt0 P carl a , 8he ? 50 5 -> 



portion of the sulphate of soda, is also dissolved, ^h'te Russian pearl ashes, 52 5S 



which contaminate the solution, and have no effect Vi- , *, Z , ,C J,U * 5 f 



as detergents. On this account, pure .oda is ccr- Ahcant barilla . 20 33 



tainly preferable for bleachi ot too lienor kinds of barilla, 10 15 



high priced,) as it contains none of the fori i rn salu ^f' .; 20 30 



contained in barilla, which retard in place of promo- Sak f taltar of the sho P S ' 72 



of bleaching. The bleachers in To these may be added the following from Mr 



Ireland fortiui Iy used large quantities of barilla, but Kirwan's tables of the composition of salts : 



