310 



NOTES AND QUERIES. 



[No. 231. 



of subinfeudation before the statute of Quia Em- 

 ptores, 18 Edw. I. A., the feoffor, reserved to 

 himself no estate or reversion in the land, but the 

 seignory only, with the rent and services, by 

 virtue of which he might again become entitled 

 to the land by escheat, as for want of heirs of the 

 feoffee, or by forfeiture, as for felony. If the 

 feoffment were in tail, the land would then, as 

 now, revert on failure of issue, unless the entail 

 had been previously barred. The right of aliena- 

 tion was gradually acquired ; the above statute 

 of Quia Emptores was the most important enact- 

 ment in that behalf. With this exception, and 

 the right to devise and to bar entails, the lords of 

 manors have the same interest in the land held by 

 freeholders of the manor that they had in times 

 of subinfeudation. (Blackstone's Comm., vol. ii. 

 ch. 287., may be carefully consulted.) H. P. 



Lincoln's Inn. 



PHOTOGKAPHIC CORRESPONDENCE. 



Spots on Collodion Pictures, §-c. — The principal dif- 

 ficulty I experience in the collodion process is occa- 

 sioned by the appearance of numberless very minute 

 spots or points over the whole extent of the picture. 

 These occurring on the whites of my pictures (posi- 

 tives) give them a rough, rubbed, appearance and want 

 of density, which I should feel obliged if any of your 

 correspondents can teach me how to overcome. 



One of your photographic querists inquires the re- 

 medy for his calotype negatives darkening all over 

 before the minor details are brought out. I had for 

 a long time been troubled in the same way, but by 

 diminishing the aperture of my three-inch lens to half 

 an inch, and reducing the strength of my sensitising 

 solution to that given by Dr. Diamond, and, in addi- 

 tion, by developing with gallic acid alone until the 

 picture became tolerably distinct in all its parts, and 

 then applying the gallo-nitrate, I have quite succeeded 

 in obtaining first-rate negatives. It is well to prepare 

 only a small quantity of aceto-nitrate at once, as the 

 acetic acid is of a sufficiently volatile nature to escape 

 from the solution, which is a not unfrequent cause of 

 the general darkening of the picture. It would be 

 well to substitute a more fixed acid for the acetic if 

 this be practicable, as it is in the collodion process, 

 where tartaric is recommended. H. C. Cowley. 



Devizes, Wilts. 



The Double Iodide Solution The great difference in 



the quantity of iodide of potassium ordered by different 

 persons, to dissolve a given weight of iodide of silver in 

 a given volume of water, has induced me to make 

 some experiments on the subject. I find that using 

 pure nitrate of silver, and perfectly pure iodide of 

 potassium (part of a parcel for which Mr. Arnold, who 

 manufactures iodine on a large scale in this island, got 

 a medal at the Exhibition of 1851), the quantity of 

 iodide of potassium required varies, cateris paribus, to 

 the extent of 15 per cent., with the quantity of water 

 added to the iodide of silver before adding the iodide 



of potassium ; the minimum required being when the 

 two salts act on each other in as dry a form as possible. 

 Take the precipitate of iodide of silver, got by decom- 

 posing 100 grains of nitrate of silver with 97'66 grains 

 of iodide of potassium ; drain off the last water com- 

 pletely, so that the precipitate occupies not more than 

 five or six drachms by measure ; throw on it 640 grains 

 of iodide of potassium ; rapid solution ensues ; when 

 perfectly clear, add water up to four ounces: the solu- 

 tion remains unclouded. But if two or three ounces 

 of water had been first poured on the iodide of silver, 

 680 grains, as I stated in my former paper, would have 

 been required, and perhaps 734. The rationale is, I 

 suppose, that in a concentrated form the salts act on 

 each other with greater energy, and a smaller quantity 

 of the solvent is required than if it is diluted. Many 

 analogous cases occur in chemistry. I hope this little 

 experiment will be useful to others, as a saving of 

 15 per cent, on the iodide of potassium is gained. As 

 a large body of precipitated iodide of silver can be 

 more completely drained than a smaller quantity, in 

 practice it will be found that small precipitates require 

 a few grains more than I have stated : thus, throw on 

 the precipitate of iodide of silver (got from 150 grains 

 of nitrate), drained dry, 960 grains of iodide of potas- 

 sium ; solution rapidly ensues, which, being made up 

 to six ounces, the whole remains perfectly clear ; 

 whereas the iodide of silver thrown down from 

 50 grains of nitrate, similarly treated with 320 grains 

 of iodide of potassium, and made up to two ounces 

 (the proportional quantities), will probably require 

 10 or 15 grains more of iodide to effect perfect solu- 

 tion, the reason being that it contained a greater quan- 

 tity of water pro rata than the first. 



The following table, showing the exact quantities of 

 iodide of potassium required to decompose 50, 100, 

 and 150 grains of nitrate of silver, the resulting weight 

 of iodide of silver, and the weight of iodide of potas- 

 sium to make a clear solution up to 2, 4, and 6 ounces, 

 will often be found useful : 



Grs. Grs. Grs. 



Nitrate of silver - - 50 100 150 



Iodide of potassium - 48-83 97-66 146-49 

 Iodide of silver - - 68-82 137-64 206-46 

 Iodide of potassium - 320 640 960 



Water up to - - - 2 oz. 4 oz. 6 oz. 



T. L. Mansell, A.B., M.D. 

 Guernsey. 



Mounting Photographs (Vol. ix., p. 282.). — J. L. S. 

 will find the " Indian-rubber glue," which is sold in 

 tin cases, the simplest and cleanest substance for 

 mounting positives ; it also possesses the advantage of 

 being free from the attacks of insects. Seleucus. 



&t$\it£ to Minor l&utviti. 



Books on Bells (Vol. ix., p. 240.). — Add to 

 Mr. Ellacombe's curious list of books on bells 

 the following : 



" Duo Vota consultiva, unum de Campanis, alterum 

 de Coemeteriis. In quibus de utriusque antiquitate, 



