THE TASTE FACTOR IN DRINKING WATER.

76 purposes. I for practical the measurement

Moderate accuracy will sumceof the dose under practical THE extensive use of X rays in the treatment of conditions cannot be made with a high degree of’ disease has brought about the necessity of measuringprecision. The correlation of the indications of the the dose administered in terms of a definite unit. dosimeter and the biological effect is the work of the A great amount of valuable work has been done at radiologist. This presents some difficulty because only different institutions all over the world in the applica- a fraction of the energy absorbed by the tissue will be tion of X rays to medicine, but hitherto, on account biologically active. A good deal of research will have of the absence of a unit of measurement, it has been to be done on the biological side to determine this. impossible to correlate the results and progress has fraction. It is well known that the X rays which are greatly suffered in consequence. Undoubtedly the scattered by tissue play an important part in the most urgent need of the radiologist at the present irradiation of deep-seated cancer. The intensity at moment is a means of accurately measuring dosage. a depth shows considerable variation according to The first step towards this is the establishment of an the disposition of the apparatus and patient and X ray unit in terms of which he can compare the the experimental conditions at the time of treatment. results of other investigators with his own. This was To obtain any degree of precision, the conditions of emphasised during an interesting discussion on irradiation must be carefully stated. For instance,. International Units and Standards for X Ray Work, the size of the field irradiated, the voltage of the which took place at the International Congress of X ray tube, the distance from and the nature of the Radiology held last week at the Central Hall, target. All these factors-and there may be othersWestminster-and reported in another part of -should be noted when measuring dosage. Prof. this issue-when representatives from all parts of WiNTZ, of Erlangen, emphasised the importance of the world were present. The subject was considered standardising these conditions so that results may be from the physical as well as the biological aspect. directly comparable. The discussion was opened by Sir WiLLx M BRAGG, To arrive at a complete solution of the problem F.R.S., chairman of the British X Ray Unit Committee, the radiologist and the physicist must work in close who dealt with the physical nature of the problem, cooperation. Already in this country and in Germany and he was followed by Dr. BECLERE, of Paris, who there exist X ray unit committees which have done valuable work in connexion with this all-important spoke from the standpoint of the radiologist. Up to the present several units have been employed question of dosage. It is worthy of note that both and confusion is likely to arise if the number of these these committees arrived independently at the units is allowed to increase. Already in this connexion same conclusion regarding the adoption of the electro-the same letter " R " denotes two totally different static unit. It is likely that several methods will be quantities. Consequently the first step towards the employed to measure the unit, so that it will be settlement of the problem is to decide upon a definition necessary to check the calibration of an instrument in of the unit which should be universally employed country against that in another country. It is all countries as a basis for the measurement of dosage. that an X ray unit committee be formed in each The unit which has found most favour is the electro- country and that these committees should keep in static unit suggested as early as 1908 by the French close touch with each other. It was resolved at the physicist VILLARD. This unit may be expressed as the close of the discussion at the Congress that an quantity of X ray energy which produces an amount international committee be formed to discuss the of electricity equivalent to one electrostatic unit in imatter further, with a view to arriving at a scheme passing through one cubic centimetre of air at 18° C. which will be universally adopted. Such an interand 760 mm. Hg. Certain factors have to be con- national committee, which will consist of both sidered when making this measurement, the chief of and radiologists, will perform an important these being that all the energy dissipated in the volume function and, as the result of its deliberations, it is of air considered is actually taken into account and hoped that research on the effect of radiation on that no extraneous effects interfere with the measure- human tissue will be greatly facilitated. ment. An absolute unit of this nature has an . advantage over other units that have been suggested, in that the dose is independent of the apparatus THE TASTE FACTOR IN DRINKING employed for its measurement. Uniformity of WATER. measurement is therefore obtained apart from any

X RAY DOSAGE.

as

.

quite

Iinone iI

urged

physicists

particular experimental arrangement. Having fixed THE British Waterworks Association held its annual’ upon the unit, the next step is to calibrate in meeting in London last week and discussed various terms of this unit the different instruments employed aspects of the water-supply. Sir ALEXANDER HousTOx,. for measuring dosage. In Germany the above unit Director of Water Examination to the Metropolitan has been employed for some time and instruments Water submitted a paper on the Purification Board, intended for medical practice have been calibrated at of London’s Water-Supply. The greater part of his a number of centres situated in different parts of the communication was devoted to the problem of taste,. country. The representatives reported that this since it is insufficient to produce a water bacterioscheme had proved quite satisfactory, an X ray dose logically safe; consumers expect also to be supplied with being reproducible at any time in the various clinics. a water free from objectionable taste. There are two There are, however, certain precautions to be taken ; kinds of taste liable to occur in town waters, chlorinous for instance, it is essential to specify the quality of the and iodoform. The former can always be avoided by radiation, as differences are observed when radiations correct or by de-chlorination, the latter is dosage of different penetrating powers are employed. In unaffected by such de-chlorinating agents as practice it has been found necessary to calibrate the sulphurous acid and sulphites. It has been known for instruments for a limited number of radiations of a long time that phenol in extremely minute doses different quality. The establishment of the physical reacts with chlorine in water to produce this extremely unit and the calibration of the dosimeters fall within iodoform taste. ADAM.31 has recently shown unpleasant the province of the physicist, and they can be carried out to a greater degree of accuracy than is required 1 THE LANCET, May 23rd, 1925, p. 1093.

77 that 1 part of phenol in 1000 million parts of water is At the same time, if very small doses of ammonia. sufficient to produce taste and that there are sufficient were found to be equally efficient as taste preventers,. phenol impurities in the atmosphere of towns to the balance might be economically in favour of supply this proportion. Water authorities using ammonia. It is clear that great progress has been,. chlorination must therefore protect their water from and is being, made in our knowledge of the reasons. atmospheric air as well as from fog, mist, rain, and why certain waters develop an iodoform taste in any liquid pollution liable to contain any trace of the presence of active chlorine, and the best and most phenol. In spite of all prophylactic measures, taste economical ways of overcoming these difficultiestroubles may still occur and must be combated. One gratifying health feature arises from these conRACE, RIDEAL, HAROLD, ADAMS, HOUSTON, and others siderations. If taste troubles can be economically and have devoted much study to this important question. certainly overcome, there will be less disposition to The three chief substances that act as preventers of cut down the dose, with consequent risk of imperfect taste in water are organic matter, potassium perman- sterilisation, in order to avoid complaints from consumers as regards taste. There have been ganate, and ammonium compounds. In the United States and Canada chlorination is cases where the question of taste rather than of nearly always practised after filtration, and it is bacteriological result was the dominant factor in, possible that taste troubles would be avoided by using determining the dose of chlorine. the chlorine before filtration. Slightly larger doses are . required, but the extra expense is almost negligible. During the last eight years 70-80 million gallons of Thames water have been chlorinated daily before filtraCONVENTION OF ENGLISH-SPEAKING tion, and no complaint of taste has been received from OPHTHALMOLOGICAL SOCIETIES. the two million consumers. Potassium permanganate THE convention of ophthalmologists to be held’ was first used by HOUSTON in 1913 to remove a taste due to Tabellaria, and later, with equal success, in next week in London is to be confined to Englishconnexion with the New River chlorination treatment. speaking societies, but one of the subjects to be conat a general meeting is the re-establishment The usual dose is 1 in 5 millions, and with waters sidered of international ophthalmological gatherings on the of surface origin the pink tinge disappears within a basis. Science knows no frontiers, and it is few minutes. Unfortunately, however, it persists to be hoped that the promoters of this discussion will even with a smaller dose in the case of deep well Meantime there is be successful in their object. waters containing hardly any oxidisable matter, thus plenty of matter to engage the attention of the conrendering such treatment practically inadmissible. vention which is to be opened by a reception at the College of Surgeons on the evening of July 13th. Permanganate has the advantage that it may be added Royal On the 14th, after the formal reception of delegates before, with, or after the chlorine with equally good from the United States, Canada, and Australia, the results. Laboratory experiments seem to show, President, Mr. E. Treacher Collins, will give the opening however, that it cannot be used before filtration if address on the Elimination of Eye Disease. This Whether will be followed by the reading of papers by various chlorination is to be practised after. or not this is due to the reabsorption of phenol members and in the afternoon by excursions tobodies during the filtration process is not known. institutions of ophthalmic interest in London and Ammonia and ammonium compounds are now being its vicinity. In the evening a reception will be held used in many places as taste preventers ; apparently at the Royal Institution of Great Britain, at which the first worker to use ammonia on a practical scale Sir William Bragg will give an address on Thomas Young and his Work. On the three succeeding days was RACE. The absence of colour is a great considerathe programme is somewhat similar. Papers will be and the for is tion, cost, weight although weight, read during the day. A symposium will be held on higher than permanganate, it may be found on further the Evolution of Binocular Vision, in which Sir study that the actual cost is less, since a smaller Charles Sherrington, Sir Arthur Keith, Sir Frederick quantity is required and also it reduces the dose of Mott, Prof. G. Elliot Smith, and Prof. S. E. Whitnall chlorine necessary for sterilisation purposes. It seems will take part; Sir John Parsons will deliver the " Bowman Lecture on the Foundations of Vision, as if ammonia, although it exercises a " lagging and there will be a discussion on the Microscopy of effect, ultimately increases the sterilising action of the Living Eye. Sir William and Lady Lister’s garden chlorine. The dose of ammonia, expressed as nitrogen, and a reception at the Wellcome Historical party required to prevent taste troubles varies in different Medical Museum will provide further opportunities cases, but 1 in 5 millions is an average figure. for social intercourse, and the proceedings are to be Sir ALEXANDER HOUSTON spoke of an experiment wound up by a banquet at the Guildhall on July 17th, on a large scale, 45 million gallons a day, in which at which H.R.H. the Duke of Connaught is to be the The organisers are to be chlorine alone was first used in a dose of 1 in 3 guest of the convention. millions. The percentage number of 10 c.cm. positive congratulated on a programme so full of interest and B. coli cultures was 26. When ammonia was added variety. The meetings are to be held at University College, Gower-street, W. C. 1. On arrival in London (1 in 5 millions) before the same dose of chlorine, every member of the convention is requested to attend the number of positives was reduced to 4. as soon as possible at the Registration Bureau. The cost per pound of liquid chlorine, liquid sulphurous acid, permanganate, liquid ammonia, and BETHLEM HOSPITAL SITE.-The Select Committee ammonia compounds (expressed as nitrogen) is of the House of Lords which has had before it the Bethlem as follows :approximately Hospital Bill authorising the removal of the asylum to the Monks’ Orchard Estate on the Kent and Surrey borders, has decided that the measure ought to proceed on the ground that there is general agreement as to the desirability of the scheme. Sir Lynden Macassey. K.C., opposed on behalf of the Southwark Borough Council, which desires to keep the site as an open space, but -Alr. Thomas, K.C., for the promoters, pointed out that the charity -would suffer if the

Ipre-war

value of the site could not be

Thus chlorine is ammonia and its

realised.

The governors,.

however, quite prepared to consult with the London County Council and to cooperate with the public-

were,

by far the cheapest chemical, j compounds the most expensive.Eauthorities.

and I