link to Talbot Project home page link to De Montfort University home page link to Glasgow University home page
Project Director: Professor Larry J Schaaf
 

Back to the letter search >

Result number 1 of 2:   < Back     Back to results list   Next >  

Document number: 7030
Date: 31 Mar 1864
Recipient: BRITISH JOURNAL OF PHOTOGRAPHY Editor
Author: TALBOT William Henry Fox
Collection: PUBLISHED
Last updated: 3rd June 2007

[The original has not been located. This version was published under the heading: 'The first use of Bromine in Photography,' The British Journal of Photography, v. 11 no. 212, 15 April 1864, pp. 127-128.]

A printed statement was recently put into my hands, addressed to all lovers of photography, suggesting that a subscription should be entered into by them with a view to purchase a life annuity for Mr. J. F. Goddard, a gentleman of well-known scientific acquirements, and now of advanced age. Of this suggestion I need hardly say that I cordially approved. But, on continuing to read further, I was surprised to see that it was proposed to give this testimonial to Mr. Goddard as having been "the first discoverer of the employment of bromine in photography."

Now, as I was myself undoubtedly the discoverer of the use of bromine in photography, I feel that I ought not to allow this error to remain unnoticed, lest it should become established in the history of the art.

My discovery was fully published at the time it was made, viz., in March, 1839. Mr. Goddard's first experiments were only made in the autumn of 1840, and first published in the Literary Gazette of December 12th, 1840, according to the statement in the printed paper, which I have no doubt may be accepted as correct. I therefore claim the priority of publication of one year and nine months.

The lapse of twenty-five years since the first public announcement of photography has caused many of the early publications to fade from the memory of the photographer of the present day; but they contain facts which are worth the attention of any one who may be engaged in writing the history of the gradual development of the art.

I shall now proceed to produce evidence, from the Comptes Rendus of the French Academy of Sciences, of the correctness of the date which I have stated.

From the Comptes Rendus, vol. viii., page 409. [sitting of 18th March, 1839.]

M. Biot communicates the following letter, which he received yesterday from Mr. Talbot: -

Sir, - I have just received the Comptes Rendu of the 18th February. Seeing there an account of the experiments which you and M. Becquerel are making on electrical and chemical radiations, I perceive the necessity of increasing as much as possible the sensibility of our means of observation, and of varying them in different ways. I will therefore describe to you a new sensitive paper which I have discovered, and which appears to me to offer some advantages.

New Preparation of a Sensitive Paper. - Take good writing paper, spread upon it a solution of nitrate of silver, then a solution of bromide of potassium, then again more of the nitrate of silver, drying the paper at the fire between each operation.

This paper is of a pale yellow colour; it is very sensitive to the light of the sky, but insensible to artificial heat, and can be held close to the fire without injuring it. Light first turns it to a bluish-green colour, then to and olive-green, then almost black.

Whether the impressions or images obtained upon this paper can be fixed in the same way as those made upon chloride of silver is a thing which I have not yet determined; but I expect it, since there is the greatest analogy between the chloride, iodide, and bromide of silver. Each of the three becomes insensible to light, having been previously very sensible, if the proportion of silver is diminished below a certain point; and in the case of each of the three this change of state is sudden. I have made many experiments on the chloride relative to this point.

As to the degree of sensitiveness of this paper I can only give it in a vague manner, from the want of a fixed unit of comparison. Here are, however, some experiments which I made on it during the bad weather which we have had during the last few days.

At four o'clock in the afternoon, month of March, dark, cloudy weather in London, it required seven minutes to obtain an image of a window with the camera obscura. The same evening, at five o'clock, with a better piece of paper, it took six minutes. In the same time the outline of any object projected against the sky would have been obtained. Some minutes after sunset, the weather being dark and very cloudy, the paper was exposed close to the window, and it required from twenty to thirty seconds to become sensibly darkened.*

After reading this letter M. Biot added the following details:-

Independently of the optical uses to which Mr. Talbot applies his new preparation, it will be very useful to physical science from the succession of colour which it passes through, for these different phases of its impressionability will offer so many characters of those portions of the atmospheric or terrestrial radiation which produce each of them. I have employed to the same end the changes of colour which radiations of different kinds produce upon guiacum resin spread in layers sufficiently thick - changes which make it pass successively from yellow to green and blue, then become yellow again, and then green again, by alternations which depend upon the kind of radiation which is made to act upon it, and of which these very changes become a special character. One arrives thus by another road at results altogether similar to those which Wollaston discovered by the solar spectrum. But my experiments on this curious subject are not yet finished.

Another particular worthy of remark in Mr. Talbot's new preparation is the high degree of impressionability we there find in a product that has been dried at a fire, and, consequently, deprived of free water, which was already the case, though not so distinctly, in the sensitive paper of M. Daguerre and Mr. Talbot.

Here, then, one meets again a phenomenon known in chemistry, and thought well worthy of attention for its molecular character, which consists in changes of relation and perhaps of combination among particles of a system already solidified.

M. Pelouze has himself given a curious example of it in the variation of tint which the atmospheric radiation produces upon the new cyanide of iron which he has discovered.

I have made for myself some of Mr. Talbot's new sensitive paper, and I have found it to possess the great sensitiveness which he attributes to it. In order to know whether the material elements of the paper contributed essentially to the phenomenon, I effected the same operations in the dark by applying the successive layers upon a plate of white unglazed porcelain, and drying them slowly over warm ashes. The product, as finally dried, was a solid dry coating of the colour of sulphur, which I kept for some hours in a closed cupboard. When I took it out to expose it to the radiation this morning about ten o'clock, it appeared of a beautiful canary yellow colour, but I had hardly time to present it to the radiation before it turned green, even in its most solid and projecting portions. It afterwards passed rapidly through all the changes which Mr. Talbot indicates.

Wishing to try if drying at the fire was indispensable in order to produce these phenomena, I placed myself in a dark room, lit only by a single candle, and I dropped one or two drops of nitrate of silver into a solution of bromide of potassium in water. There formed immediately a solid precipitate, which was no doubt bromide of silver; it appeared to me white by the light which I employed. I separated the excess of bromide by decantation, and I threw the precipitate upon a porcelain plate, where I left it to dry spontaneously. There resulted a powder which appeared to me white, but having taken up some small portions of it on paper and on a slip of horn, I had no sooner opened the door of the room to expose it to the light, that it appeared to me to be of a canary yellow colour, and I had hardly time enough to note the phases of its passage to yellowish green, and then to olive green, nearly black.

[The rest of the precipitate which had dried spontaneously on the porcelain plate in the dark had the next day an impressionability perhaps still greater. - Note by M. Biot.]

I then thought that the solution of the two salts in water was perhaps not indispensable in order to give to the product resulting from their mutual reaction this great sensitiveness. I therefore ground successively in an agate mortar a little nitrate of silver and bromide of potassium, in a dark room. Both powders observed separately appeared to me white, and their mixture likewise; but having placed a small portion on a paper I had no sooner left the room than these little heaps of powder appeared to me of a canary yellow, and the atmospheric radiation made them pass almost instantaneously through all the phases which had been presented both on paper and porcelain by the product resulting from the successive application of the two salts in a state of solution. Are there not probably other combinations more numerous than are commonly supposed which, when formed in the dark, possess proper colour, different from those which are generally attributed to them from not having prepared or studied them, except after they have received an impression from the atmospheric radiation? This is a conjecture which I submit to chemists.

I have translated the preceding as literally as possible from the Comptes Rendus.

H. Fox Talbot.

Edinburgh, March 31st, 1864.

*The reader will please to remember that in March, 1839, when this paper was written, the process of developing a latent image upon photographic paper was unknown, not having been discovered by me until September, 1840. Had it been known to me in 1839, the times here specified would have been diminished 100 or 00 times.

Result number 1 of 2:   < Back     Back to results list   Next >