91 THURSDAY, 18th JANUARY, 1917. (At Perth). Present: Charles Edward Dempster, Esq., Chairman. Matthew Thomas Padbury, Esq Ranald McDonald, Esq. EDWARD ALEXANDER MANN, Government Analyst, further examined: 1003. By the CHAIRMAN: We understand you wish to amplify the evidence you have already given on oath? — Yes. i simply wish to make a further statement which I submitted to you in writing on the 13th January. It is as follows:— There is one technical matter which I would like to explain lest a false impression should have been taken by members of your Commission, although it would be readily understood by chemists it is possible that some of the figures which I put before you may be misunderstood. Chlorine which occurs in any soil may be associated in combination between lime, potash, soda, magnesia, etc., and when one speaks of chlorides in the soil that term will include any one of the four compounds — chloride of lime, chloride of potash, chloride of soda, chloride of magnesia. The chlorine is very easily and accurately estimated while the base with which it is combined is not so easy of determination, nor is it possible to declare with accuracy what proportion of the chlorine is combined with these various bases. It is, therefore, customary in soil analysis to determine the chlorine exactly and then to calculate it into the corresponding amount of chloride of sodium (common salt). This is done for two reasons — (1) the chloride of sodium is the most widely distributed of these salts, and (2), sodium chloride being the most harmful, the valuation of the soil on the basis of its common salt content affords the greatest margin of safety. This method of working is always indicated in reports of soil analyses by using the words "Chlorine as Sodium Chloride," which indicates to any chemist that chlorine has been estimated and calculated as "Sodium Chloride". It is well to make clear that this is the meaning of the use of the expression "Sodium Chloride" in all my evidence and reports to the Commission, and it must be taken, therefore, to indicate that I do not definitely state that all the chloride found is present as chloride of sodium; it may be partly in the other forms which I have referred to., viz Potassium Chloride, Magnesium Chloride, or Calcium Chloride. At the same time I beg you to note that all these compounds are harmful to wheat crops, though in varying degrees. The latest experimental figures showing the results of observations of their effects upon wheat in coarse sand give the following results:— Percentage of salt in coarse sand giving about half normal germination and production of dry matter in wheat: Chloride of Sodium, .2 per cent.; Chloride of Potassium .25 per cent.; Chloride of Lime, .3 per cent.; Chloride of Magnesia .4 per cent. In some of the correspondence you will find the question of the possible presence of chloride of magnesia referred to me and that I replied that it was more harmful than common salt. That was always considered to be a fact on the data we had. Some experiments have since been carried out in America and these experiments indicate that chloride of magnesia is less dangerous than it was thought to be. Therefore, on that point I have to modify the opinion I have expressed in the correspondence. The written statement continues;— This will explain the meaning of the fourth last paragraph in the statement submitted by me to the Commission on my hearing, in which I refer to the less deleterious effects in the soil owing to the varying proportions of lime and magnesia, and it maybe found that on some of the soils containing large amounts of chlorine the fact that crops may be grown is due to the chlorine being combined with lime or magnesia. In the conditions which exist in soil solution, where these compounds are present in varying proportions, and where various interactions may occur between them, it is almost impossible to state with exactness the different proportions of these compounds which may present in the solution from time to time and under varying conditions. This is an additional reason why crop experiments were recommended by me, and I think it necessary to make this explanation, as otherwise the Commission may have misunderstood my evidence, but I was anxious not to confuse the matter by over-much technical explanation.