Is nibtc stable in acid

1. In acidic environment, electroless nickel plating can be carried out in a solution containing only nickel ion and hypophosphite. However, in order to stabilize the process, nickel ion ligands are necessary in alkaline electroless nickel plating solution to prevent hydroxides and

2. (5) The stabilizer electroless nickel plating solution is a thermodynamically unstable system. In the plating process, if local overheating is caused by improper heating method, or local pH value is too high e to improper bath adjustment and supplement, or impurity is introced or formed e to bath pollution or lack of sufficient continuous filtration, intense autocatalytic reaction will occur in the local part of the plating solution, A large amount of Ni-P black powder is proced, which makes the bath decompose in a short time. Therefore, stabilizer should be added to the bath. The function of stabilizer is to inhibit the spontaneous decomposition of plating solution and make the plating process orderly under control. The stabilizer can be preferentially adsorbed on the surface of the particles to inhibit the catalytic reaction, thus masking the catalytic active center and preventing the nucleation reaction on the surface of the particles, but it does not affect the normal electroless plating process on the surface of the workpiece. However, it should be noted that the stabilizer is a kind of toxic agent for electroless nickel plating, i.e. a reverse catalyst, which can inhibit the spontaneous decomposition of the plating bath only by adding trace amounts. The stabilizer should not be used too much. If the stabilizer is used too much, the plating speed will be reced. If the stabilizer is used too much, the plating speed will not be increased. The stabilizers commonly used in electroless nickel plating are as follows. ① Heavy metal ions, such as Pb2 +, SN2 +, Cd2 +, Zn2 +, Bi3 +, etc. ② Compounds of group VI a elements s, Se, Te, such as thiourea, thiosulfate, thiocyanate, etc. ③ Some oxygen-containing compounds, such as AsO2 -, m0042 -, N02 -, IO3 - and so on. ④ Some unsaturated organic acids, such as maleic acid 6) The composition of accelerating agent in electroless nickel plating solution which can improve the nickel deposition rate is called accelerating agent. The mechanism of its action is believed to be to activate hypophosphite ion and promote its release of atomic hydrogen. Many complexing agents in electroless nickel plating also act as accelerators. F in inorganic ions is a common accelerator, but its concentration must be strictly controlled. Large amount of F will not only rece the deposition rate, but also affect the stability of the bath. The research shows that many substances used as stabilizers in electroless nickel plating bath can act as accelerators when they exist in more trace amounts in nickel plating bath. When the dosage of thiourea is 5mg / L, it acts as a stabilizer. When the dosage is reced to 1mg / L, it acts as an accelerator 7) Other components in electroless nickel plating solution, in addition to the above main components, sometimes add surfactants to inhibit the pinholes of the coating, and add brighteners to improve the brightness of the coating. However, sodium dodecyl sulfate is not suitable for electroless nickel plating because it often causes incomplete stains on the coating

3.

(1) Constant component

test shows that HCO < sup > - < / sup > < sub > 3 < / sub >, CO < sub > 3 < / sub > < sup > 2 - < / sup >, so < sub > 4 < / sub > < sup > 2 - < / sup >, CI < sup > - < / sup >, K < sup > + < / sup >, Na < sup > + < / sup >, CA < sup > 2 + < / sup >, Mg < sup > 2 + < / sup > in various hydrochemical types of groundwater with total dissolved solids (formerly known as salinity, TDS) less than 2000mg / L, The influence of the storage days of water samples at room temperature on the determination results is as follows: when 20 days, the contents of HCO < sup > - < / sup > < sub > 3 < / sub >, CO < sup > 2 - < / sup > < sub > 3 < / sub >, CA < sup > 2 + < / sup >, Mg < sup > 2 + < / sup > change slightly; At 30 days, the content of major components in other hydrochemical types of water samples did not change significantly, and the container had no obvious effect on the stability

for the water samples with total dissolved solids of 2000-6000 mg / L, only special carbonate bicarbonate mineral water was found. Due to the separation from the original water body, the carbonate balance system was destroyed. Compared with the field analysis results, the pH value, free CO < sub > 2 < / sub >, HCO < sup > - < / sup > < sub > 3 < / sub >, CO < sup > 2 - < / sup > < sub > 3 < / sub >, HCO < sup > 2 - < / sup > < sub > 3 < / sub >, CO < sup > 2 - < / sup > < sub > 3 < / sub >, HCO < sup > 2 - < / sup >, HCO The content of Ca < sup > 2 + < / sup > changed greatly. The contents of major components in other hydrochemical types of water samples did not change significantly within 20 days, nor did the containers

(2) nitrogen compounds can be divided into inorganic nitrogen and organic nitrogen. There are ammonium ion, nitrite ion and nitrate ion in inorganic nitrogen; Protein, amino acid and nitrogenous organic compounds are the main components of organic nitrogen

In nature, e to the action of nitrifying bacteria, organic nitrogen is usually hydrolyzed:

rock and Mineral Analysis Volume 4 resources and environment investigation and analysis technology

nitrate ion, the final proct of this change, is stable

The results showed that the transformation of three forms of inorganic nitrogen compounds existed when they coexisted in water samples. No < sup > - < / sup > < sub > 3 < / sub > was the most stable when the temperature was high (29-33 ℃), and there was no significant change after 30 days of storage; NH < sup > + < / sup > < sub > 4 < / sub > was stored in a hard glass bottle without significant change within 10 days. Only no < sup > - < / sup > < sub > 2 < / sub > changes the most, and the loss can reach 15% - 26% in only 12 hours; However, it did not change within 24 hours when the pH was less than or equal to pH 2. Therefore, the content of no < sup > - < / sup > < sub > 2 < / sub > should be determined immediately after the water sample is opened. The results showed that the contents of three nitrogen compounds (0.05-20 mg / L) did not change significantly in 5 days in low temperature area

(3) f < sup > - < / sup >

F < sup > - < / sup > is the stable valence state of fluorine. According to the relevant data at home and abroad, the fluorine in water samples can be effectively stored for 7 days by adding NaOH to pH 11 or at 4 ℃. The experimental results show that the water samples containing F < sup > - < / sup > 1 ~ 4mg / L with total dissolved solids of 0.1 ~ 2.0g/l are stored as they are or at pH 2 ~ 11. No obvious change is found in glass or polyethylene containers after 30 days. The highly mineralized brine containing F < sup > - < / sup > 10mg / l was preserved as it is and had no obvious change within one month; Compared with the results of 30 days, the relative error of 1 day is less than 0 ± Within 3%

(4) Br < sup > - < / sup >

experiments show that the stability of BR < sup > - < / sup > in water samples is greatly affected by the total dissolved solids and container materials. When the groundwater containing 1mg / L br < sup > - < / sup > and the salinity up to 2G / L, or even the brine containing 3mg / L br < sup > - < / sup > are sealed as is or stored at pH 2-11 for 10 days, no loss is found; At 30 d, Br < sup > - < / sup > of the former only slightly lost at pH 11; However, no loss of BR < sup > - < / sup > was found in brine

in the groundwater with low total dissolved solids (≤ 1g / L) and Br < sup > - < / sup > 1mg / L, no loss has been found after 5 days of storage under the same conditions as above. At 10d, the content of BR < sup > - < / sup > stored in hard glass container had no loss; When stored in polyethylene container, the loss of BR < sup > - < / sup > reached 17% - 23% except the original sample. Therefore, Br < sup > - < / sup > should be stored in hard glass container

(5) the results of I < sup > - < / sup >

test show that when the hard glass container is sealed, the total dissolved solids is 2G / L, and the groundwater containing I < sup > - < / sup > 0.03mg/l has no loss within 10 days; However, the groundwater with total dissolved solids less than 1G / L and I < sup > - < / sup > 0.3mg/l has no loss. By 10d, the loss of I < sup > - < / sup > has reached 10% - 30%

(6) HBO < sub > 2 < / sub >

boron often exists in the form of anion in water, which is relatively stable. The groundwater contains mg of boron, which is stored in polyethylene container as it is. After 30 days of storage, the result has no obvious change

(7) Po < sub > 4 < / sub > < sup > 3 - < / sup >

there is little phosphorus in groundwater. The groundwater containing 0.3 mg / L phosphate and less than or equal to 1 g / L of total dissolved solids was respectively stored in glass or polyethylene containers at pH 2-11; At 3 days, the loss of phosphate in glass container was 26% at pH ≈ 11; The loss of phosphate radical in polyethylene container is 56%. Under other pH conditions, no loss of phosphate was found. When the storage time reaches 10 days, the best preservation effect is pH ≤ 2 and chloroform in the original sample. At this time, compared with the first day, the relative error is ±( 1.7%～8.1%) Under other conditions, there are different losses. When stored in nitric acid medium with pH ≤ 2, there was no obvious change within 30 days

The phosphate in bicarbonate mineral water with total soluble solids of 2G / L and Ca < sup > 2 + < / sup > content up to 0.6g/l is still stable at pH ≤ 2 for 15d; Under other conditions, the loss has reached 60%

(8) as, Se, Mo

natural water contains little as, Se and mo. They exist as anions in water. For the water sample containing 0.2mg/l arsenic, under the condition of sealed storage, the test results show that there is basically no loss within 5 days, and the loss is up to 25% within 15 days. When stored in acid condition with pH ≤ 2, there was no significant change within 30 days

for the water sample containing 0.06mg/l molybdenum, only 5% of the water was lost within 30 days when it was stored in the original sample and pH ≤ 2, and the glass container was better than the polyethylene container

the water samples containing 0.1mg/l selenium were stored under the conditions of original sample (pH = 7.3) and pH ≤ 2, respectively, and there was no obvious change within 15d

(9) the analysis and determination of Fe < sup > 3 + < / sup >, Fe < sup > 2 + < / sup >

is of great significance for understanding the redox environment of some geological units; At the same time, many technical water also requires analysis results of Fe < sup > 3 + < / sup > and Fe < sup > 2 + < / sup >

At present, the relevant data at home and abroad advocate that the water containing iron should be preserved in nitric acid medium with pH ≤ 2. This method is effective for the determination of total iron. Nitric acid can not be used as a protective agent for Fe < sup > 2 + < / sup > because of its oxidation. According to the comparative experiments, the addition of sulfuric acid ammonium sulfate protective agent can protect the Fe < sup > 2 + < / sup > (even up to 22mg / L) in groundwater of various water quality types and different dissolved total solids. Within 80 days, its content was stable without loss. In acetic acid buffer (pH ≈ 4) medium, it can only be effective for water samples with Fe < sup > 2 + < / sup > less than 3mg / L

(10) the stability of chromium in water is related to its valence state. The water samples containing Cr < sup > 6 + < / sup > 0.05mg/l were stored in hard glass or polyethylene container in neutral environment, and were basically stable within 30 days. When stored in acidic environment with pH ≤ 2, the content of hexavalent chromium graally decreases with time e to its strong oxidation. The loss of hexavalent chromium reaches 30% in 3 days and 90% in 30 days

The contents of

total chromium, Cr < sup > 3 + < / sup > and Cr < sup > 6 + < / sup > in neutral water samples were decreased with the increase of storage time e to the hydrolysis of Cr < sup > 3 + < / sup >. The loss was 8% on the second day after sampling; After 30 days, the loss reached 75%. The total chromium content remained unchanged after 30 days of storage at pH ≤ 2. Therefore, when CR < sup > 6 + < / sup > is determined, the sample should be taken from the original sample (neutral); When determining total chromium, acidified water sample should be taken

(11) the speciation of heavy metal ions in water samples is very complex. In addition to simple ions, they also exist as hydroxides, sulfides, carbonates, colloids and complexes. Therefore, if the water sample is placed without treatment, various forms of heavy metals in the sample will be adsorbed by the suspended substances and agglomerated, or will adhere to the wall or bottom of the container. Therefore, many literatures at home and abroad suggest that it should be stored in nitric acid medium with pH ≤ 2

the storage conditions of water samples containing Cu, Pb, Zn, CD, Fe, Mn, Co, Ni and Hg (0.05-1.0 mg / L) were studied. The results showed that when the water samples were stored at pH ≈ 7 (i.e. original sample), except for Zn and CD, the losses of other elements were small in 15 days, and the losses of CO and Ni were as high as 97% - 100%. When pH ≈ 4, the results also decreased significantly. Only in the medium of pH ≤ 2 can it be stable. At this time, Hg can be effectively stored for 7 days, and the determination results of other items are basically unchanged within 15 days

The trace elements such as Li, Rb, Sr and CS can be determined from the original sample. When atomic absorption spectrometry is used, samples can be taken from acidic water samples for analysis. In addition, in order to rece the number of sample containers, radioactive elements such as u, th and RA can also be determined in acidic water samples

(12) soluble silicic acid

the content of soluble silicic acid in natural water varies greatly with different geological conditions, and silicic acid presents three forms in a certain equilibrium relationship α Type γ Type β There was no significant difference between the two groups. When the external conditions change, they will polymerize or transform. The experimental results show that when the soluble silicic acid in water sample is about 100mg / L, the content change is only 6% within 27 days after being stored in the original sample and in the acidic environment with pH ≤ 2. When the concentration of silicic acid was 250 mg / L, the loss of silicic acid began to occur after 3 days in the original sample, and the loss amount reached 50% - 60% after 10 days; However, when stored in hydrochloric acid or nitric acid with pH ≤ 2 for 24 days, there was no obvious change

(13) phenol and cyanogen are general, and the content of phenol and cyanogen in natural water is very small and unstable. When the phenol and cyanogen in the water sample were kept in the medium with pH ≥ 2, the phenol of microgram level began to lose after 2 days; No cyanide loss was found within 3 days; The results of sampling with hard glass bottle are better than those with polyethylene

Radon is a kind of radioactive gas. It has a certain solubility in water, but is easy to be adsorbed by solid substances. Therefore, it is not allowed to use absorbent utensils, such as metal bottles, rubber stoppers and rubber tubes; We can't use polyethylene plastic container to hold samples, otherwise the result will be low. When sampling, it is also necessary to avoid stirring the water sample to prevent radon from escaping from the water

4. 1. Potassium permanganate is much more oxidizing in acid than neutral or alkaline, and the rection proct is almost colorless Mn2 +, which is convenient for experimental observation. Therefore, acid potassium permanganate is generally used in "identification test"
(Note: in the case of "Organic Preparation Experiment", it is better to use alkaline potassium permanganate, because the rate of oxidation of organic matter by alkaline potassium permanganate is fast! The oxidizability is a thermodynamic factor; The speed of oxidation reaction is the kinetic factor!)< Sodium hypochlorite proces hypochlorite under acidic conditions, which is easily decomposed into Cl2 or O2 and is not easy to preserve
on the other hand, the oxidation of sodium hypochlorite is not greatly affected by the pH of the solution

why not use basic KMnO4 to oxidize Fe (OH) 3 to prepare FeO42 - or Ni (OH) 3
A: This is because KMnO4 has weak oxidizability under alkaline conditions, and can not oxidize these two substances< However, the oxidation of FeO42 - or Ni (OH) 3 is stronger than that of KMnO4 in acidic condition,
so KMnO4 can not be used at all
sodium hypochlorite should be considered at this time,
because the oxidation of sodium hypochlorite in acidic and alkaline conditions has little change,
but if the oxidation proct FeO42 -, Ni3 + in acidic conditions is stronger than HClO,
so NaClO should be used in alkaline conditions

5. Most metal ions begin to precipitate or even precipitate completely under acidic conditions
for example, SN2 + and Al3 + precipitate completely at pH ≈ 5 (the concentration of resial ions in the solution is less than 0.00001 mol / L)
while Fe3 + precipitates completely at pH ≈ 4
others such as be2 +, Cu2 +, Zn2 + are pH & gt; Fe2 +, CO2 + and Ni2 + began to precipitate at pH 5; They precipitate completely in alkaline environment
Ag + and Pb2 + begin to precipitate almost at pH ≈ 7
the most ferocious ions such as Sn4 + are found at pH & lt; It has completely precipitated at 1:00
among the common metal ions, only Mg2 + and Mn2 + can begin to precipitate in alkaline environment
the reason why H + and NO2 - can not coexist is that they combine to form HNO2, which is very unstable and will decompose rapidly after formation: 3hno2
=
2No ↑
+
HNO3
+
H2O. NO2 - can only exist stably in alkaline condition.

6. Yes
the carboxyl group in formic acid is quite stable and will not be reced, but formic acid also has aldehyde group. Aldehyde group can be reced to hydroxyl group in the presence of Ni catalyst. The reaction equation is as follows:
HCOOH + 2h2 - Ni catalysis → CH3OH + H2O
(the reaction principle is that the aldehyde group in formic acid first turns into hydroxyl group, because two hydroxyl groups cannot exist on one carbon atom at the same time, the two hydroxyl groups dehydrate and then turn into one aldehyde group. The aldehyde group is reced again and finally becomes methanol.)

7. Satisfy charge conservation